1.33x seems fine as of the 22nd Budokai to me. Yamcha's Rogawhohoken seems to pack some kind of amp and the fact that he labeled the one used against Ten Shin Han as "2.0" might mean it's perfected above the initial. The KMHMH from Yamcha seems to be his trump card, so it's even above the Rogawhowhoken 2.0.
The Super KMHMH should have even more of an amp and was described as a huge one. Still, somewhat below the one employed against Raditz, which reached the 2.2x mark.
Initial KMHMH (used by Goku at Pilaf's domains) -- 1.05x
21st Budokai (used by Goku and Roshi) -- 1.15x
Yamcha Rogawhohoken -- 1.1x
Yamcha Rogawhowhoken 2.0 -- 1.2x
KMHMH at the 22nd Budokai (maybe Goku's and Kame's contain a multiplier bigger than Yamcha's but I will assume not for simplicity) -- 1.33x
Super KMHMH -- 1.65x
It's weird that the Super KMHMH containing all this amp didn't have an effect on Piccolo Junior, though. Some ppl like to assume Piccolo's blast had a cushion effect, softening the blast's strength.