Yes I agree, Piccolo is using effort and easily handling Gero but Gero is able to bounce back pretty well. Piccolo > Gero is a smaller gap than Freeza's 2nd Form FP > Piccolo Weighted imo. By a good margin.
Also, Krillen was able to chop off Pirate Robot's hand, so chopping off a robotic hand doesn't seem to be that big of a feat.
I was going to do the base powers on that list but I ran into major, major problems.
Want to now a fucked up chain that just messes up everything here? Check it out...
20 Post ( Yamcha, Vegeta's Blast, Piccolo Suppressed ) - Piccolo ( Suppressed ) = 20 Post ( Yamcha, Vegeta's Blast )
Seeing how it doesn't seem all that possible for 20 Initial to be all that much weaker than 20 Post ( Vs Piccolo ), it does appear that Piccolo's suppressed power, which brings into the base and human powers... Finish in a little.