I hate to differ but we flew a 120 Stinger for a couple of years with a 45 (firewall beefed up of coarse) and the only consequence we observed was the plastic on the T.D. where we screwed it to the fuse started spliting.

I have flown the 45 on the following planes with no problems (other than way overpowered).

H9 1/4 Edge
H9 1/4 Cap
Texas Hurricane
120 Stinger & the Giant Stinger
Bridi Big Bee

It also works pretty good in a H9 Taylor craft that I saw used to tow gliders.