I had a YS 63 in my arf SE and it flew awesome. I took the engine out and am in the process of installing a Irvine 72 in mine, just because I want to see what will happen.

The 4-stroker was quite an engine. It had plenty of power to do just about anything, I just got tired of dragging around an extra gallon of fuel just for that plane, so I am trying something new.