Why not a little extra suds ? Sure, the Ryan will fly with a .90 4-popper, or even an .75 2-stroke.
But it's a good sized plane...and not light.
I have a STA in the pile, with a Magnum 1.20 4-pop.

If some extra weight is needed up front, it would be silly (IMHO) to under-power the craft. I heard somewhere....that in powered-planes, the key word is "power".

I don't see anything wrong with some great verticle....a nice hammer-head...some monster loops. I think a guy with the .90, and the extra needed weight....would be wishen' he put in the 1.20.