THose engines can not be compared really, I have all the models you talk about, the 61RE (OS) y have is really a beast on the 60 size with a good pipe, but the YS63 is way more powerfull than the OS61FX and it weights 200gr less, it sounds like any other bigger YS, the YS110 is a beast on the 100-110 side, weights as much as any 91 2 stroke, but the power......, but until is fully broken in it is not a simple engine to operate, the YS110S should be totally different if it behaves like the 63S.

If your airplane flies with a 61 you can put the YS63 and it will have power to spare, but if the aircraft was designed or intended for the OS61 Hanno for example I will go with the 110.

Maybe Mike McConville can ask Peter Goldsmith for you?

Regards