YS 63
 

They are really good and I think they would be great for your 40 sized pattern plane.

What is the best 4 stroke for this application??
 

YS- perfect for pattern power period !
Tank can go right on the CG, the transition is flawless and much better than Saito. Lower idle easy starting. Weight is within a couple ounces of the Saito power is a bunch better. The YS has a very strong midrange and sags less when pulled vertical There are FAR more pattern flyers with YS engines than Saito for a reason!
The YS is a VERY user friendly engine ....VERY ! Set em and forget em. Competition flyers wouldn't use YS if they required fiddling. When you start flying competition you will find you have NO TIME TO FIDDLE ! Most club events supply 20% fuel and the YS is happy with that. Horizon highly reccomends 30% for the Saito. They run on 20 but still don't supply the power of the smaller YS.
Learn the YS ,you'll be glad you did . From idle thru midrange to peak power they smoke the Saito !

I own BOTH !