Humans in the story

[Bussani]

If goku fires several kamehameha he will be exhausted as well.

And if he fired one massive Super Ultra Kamehameha that used all of his energy, it would probably be similar to a Kikoho. Normal Kamehamehas weren't made to be that big though, I think. It wasn't until the 23rd tournament that Goku had come up with a 'Super Kamehameha' variation.

SK increases the force of the Kikoho meaning that SK is an amplification of a previous technique the Kikoho.

Or just that Tenshinhan is so much stronger now that he can power it. I'm not disagreeing with your theory, just pondering that it isn't the only option. Personally, I like the idea of mixing the theory of Kaioken with Kikoho to make something better.

Tenshinhan used a small kikoho to make a small hole in the 23 world tournament to protect everyone,so it seems you can use it without using everything you have.

Yes, he did show that you can control how much power you put into it. If he didn't, he would have killed himself when he used it in the 22nd tournament. You just want to use as much as possible if you want it to be as big as possible. What's the point of using it as a finishing attack if you hold back too much?

Whether Shin Kikoho was bigger or not, its main strength seems to be that it can be fired over and over before draining all your ki. This probably makes sense, considering how much more ki Tenshinhan has at that point to play around with.

[temujin]

And if he fired one massive Super Ultra Kamehameha that used all of his energy, it would probably be similar to a Kikoho.

My point precisely.

Or just that Tenshinhan is so much stronger now that he can power it. I'm not disagreeing with your theory, just pondering that it isn't the only option. Personally, I like the idea of mixing the theory of Kaioken with Kikoho to make something better.

It is stated in the attack guide translated by herms.
SK and Kikoho are slightly different .
According to that guide SK increases the force of the Kikoho,so it's not my theory.Take it as you like,but it seems that Sk is a better stronger version than kikoho like super kamehameha is a stronger version from a regular kamehameha,the difference is that Kikoho can be fired a single time and SK several times according to the attack guide.
Despite Tenshinhan's power increase he could not use a regular Kikoho more than a single time.

[Bussani]

My point precisely.

Then 'amplifying' the ki isn't necessary. You simply need a technique that can fire a massive amount of your ki.

It is stated in the attack guide translated by herms.
SK and Kikoho are slightly different .
According to that guide SK increases the force of the Kikoho,so it's not my theory.Take it as you like,but it seems that Sk is a better stronger version than kikoho like super kamehameha is a stronger version from a regular kamehameha,the difference is that Kikoho can be fired a single time and SK several times according to the attack guide.

I never said that the two techniques were different. I get why we have different opinions though (see below).

Despite Tenshinhan's power increase he could not use a regular Kikoho more than a single time.

I see it differently. Attacks in Dragon Ball seem to have limits to their size. For instance, a regular Kamehameha could never match a regular Kikoho. A Kamehameha that fired all of your energy and matched the power of Kikoho would be a new variation of a Kamehameha (Super Ultra Kamehameha, for lack of a better term).

Likewise, I think that a regular Kikoho has a limit, and wouldn't always just use all your ki. As such, the Shin Kikoho variant could be a stronger version of Kikoho that can be fired rapidly, simply because you have such an abundance of ki that it's possible at that point. That's just another theory.

Edit: Like I said, though, I like the Kaioken theory. Imagine if he could maintain Kaioken x20 (or just use it over and over before firing). Theoretically it would give him enough ki to fire 10 double-sized Kikohos.

[temujin]

Then 'amplifying' the ki isn't necessary. You simply need a technique that can fire a massive amount of your ki.

Powerful or signature Ki attacks always can fire a massive amount of your ki,however, some are more powerful than others.
A regular Kamehameha could never match a regular Kikoho in equal conditions,cos,Kikoho is just more powerful than a Kamehameha.
When a Z-warrior uses a ki attack there is always a ki amplification.
That's why they use ki attacks when they can't beat their foes hand to hand,however,the user still needs to have a certain degree of power and ability to use it.

[Bussani]

Then 'amplifying' the ki isn't necessary. You simply need a technique that can fire a massive amount of your ki.

When a Z-warrior uses a ki attack there is always a ki amplification.

Well, yeah, but there's a difference between just raising your ki and something like Kaioken. There's a limit to how far you can raise your ki using the normal method. That's just 'powering up' or 'bringing your power out' as they call it. Raising your ki to your maximum power; the difference between standing around relaxed and getting ready to fight.

Using all of your ki at once would still kill you, as Vegeta showed us when he tried it against Buu.

[temujin]

Then 'amplifying' the ki isn't necessary. You simply need a technique that can fire a massive amount of your ki.

When a Z-warrior uses a ki attack there is always a ki amplification.

Well, yeah, but there's a difference between just raising your ki and something like Kaioken. There's a limit to how far you can raise your ki using the normal method. That's just 'powering up' or 'bringing your power out' as they call it. Raising your ki to your maximum power; the difference between standing around relaxed and getting ready to fight.

Using all of your ki at once would still kill you, as Vegeta showed us when he tried it against Buu.

Yes, there is a difference between kaiohken and raise ki.
However, that doesn't change the fact that both increase base power or allow to the user expand his power level further than in his base form.
It is true that vegeta died using all of his ki once,probably his technique was similar to kikoho,but with SK Tenshinhan used all his ki several times without dying.

[Bussani]

It is true that vegeta died using all of his ki once,probably his technique was similar to kikoho,but with SK Tenshinhan used all his ki several times without dying.

What I'm saying is that there's no evidence that Shin Kikoho uses 'all of your ki' to fire one. Logically, doing that should kill you.

The way I see it, the answer might be this. Imagine that Tenshinhan originally had 10 ki points at the 22nd tournament. A maximum Kikoho would be a 10 in power, but he'd want to make it a 9 to leave him enough to live.

Cell saga Tenshinhan, on the other hand, might have 10,000 ki points instead. Let's say that a Shin Kikoho is a 1,000 as opposed to a 10. With that much ki available, Tenshinhan would be able to fire it 10 times in a row before collapsing. So there you have an attack far more powerful than the original Kikoho, and rapid fired to boot.

The above numbers are just an example, don't take them too seriously.

Even if you multiplied your ki using Kaioken, if you then fired all of it, you would still kill yourself. So the only other option I can imagine is if he gathers a fraction of his overall ki between his hands, ready to fire, then uses Kaioken on only his hands to make the attack bigger than a regular Kaioken. Then do that over and over to rapid fire.

I don't know which theory is better. My point is that you can come up with a lot of different theories.