The 40LA is enough engine for this plane. If you're going to spend the bucks on a 46, why not put it on a better platform? Like an Aresti for learning pattern or a Sig SE for wild aerobatics. I've run a few gallons of fuel through my Avistar (hey that takes a while - those 40LA's don't use much fuel!) and haven't had the urge to put a hotter engine on it. It's much too limiting to really learn aerobatics on.

(asbestos suit on).

No, really. Just put together a better aerobatic platform. If you like fun-flying, I'd highly recommend the Morris Hobbies Morris the Knife. What a boatload of fun those planes are! Check out the threads in the fun fly forum. They're very easy to fly on low rates. They can fly so slow you think they'll just fall out of the sky. Great 3D trainers. www.morrishobbies.com

PS: If you get the ARF, take your time installing the servo rails. It takes some patience.

just my $0.02.