I also like the fast throttle response of the 4s engines, but I have a 55AX on a Mojo 40 and the throttle response is super. It took about 2 gallons to become very good but no complaints now!!! I have a Saito 100 on a MoAss that is waiting for decent weather to maiden. Cant wait!!

I believe either a 2S or a 4S can perform very good at 3D if tuned properly.