No, that's impossible. Kid Goku can't be only twice as powerful as that Farmer (PL 5) from DBZ. A professional athlete might have a PL of 10, Mr. Satan and Videl might have a PL between 10 to 15 and none of these people can do what Goku was doing in the very beginning of DB.
You are assuming power levels are linear, and that someone with a battle power of 10 is just twice as strong, fast, etc. as someone with a battle power of 5. The series plainly shows this to be wrong. Many times.
And Goku was doing this before any real martial arts training, and long before he learned to control his ki. You can't compare that to charged ki blasts (i.e. Master Roshi and Piccolo blowing up the moon). It's not the same thing.
This is exactly why I wouldn't rely too much on these guidebooks for information.
Yeah, I can actually. Piccolo at 408 can casually flick his wrist and blow up the moon. Goku can sit there and take Piccolo's strongest ki attack head on, even as the island around him is obliterated. King Piccolo, who is stronger than Roshi at 139, and thus not many times weaker than Piccolo, can only destroy a city, which is trillions of times less impressive than destroying the moon. Raditz took a less-than-casual blast from Piccolo with no harm at all, then proceeded to pound him with his bare hands. Yet those guys were only 80-300 times stronger than a regular human? Goku at 8,000 could fly 1,000,000 km in less than a day, even though that would only make him 1600 times faster than a fat farmer. Wow, this is all a load of BS, the manga is obviously wrong, I wouldn't rely on it too much for information.
The assertion that kid Goku had a PL of 10, with no proof whatsoever, is indeed something that someone pulled right out of their ass.

And it's much better to rely on the manga for information, not silly fan theories.
And the manga never says that he can't be 10, and goes out of its way to show that power levels are not linear. Repeatedly.
Also, you seem to be incapable of looking at anything other than just a set of numbers. Even if Goku only had twice as much ki as the farmer (which isn't true), he still would've been much physically stronger on part of being an alien that is meant to survive in x10 Earth's gravity. Battle power is a measurement of ki, it has nothing to do with physical strength.
You mean silly fan theories like what you're spouting right now?