RE: Koas 40
I flew my (and I'll probably get crap for being a cheapskate) first Tower Kaos 40 with a Tower Hobbies .46 and on my second Tower Kaos on a GMS .47 and both performed great with plenty of power authority to pull through the beginning and intermediate pattern maneuvers without issue. Dropping a .54 or larger into the airplane basically will turn it into a brick when the engine quits in my opinion. But there again it's my own opinion. Airplanes should fly on the performance of what the wing and engine provide and not just where one points the engine.
Modern day engines developed much more power then what they did 3 decades ago....
Cheers,