I agree that the .90 or .91 has more power in the same size/weight as the .61 or .75s but the pipe required is quite a bit bigger for a 90 sized motor. The 60-75 sized motors call for a 10cc pipe and the 90 has to jump up to a 15cc pipe. But hey, I still may opt for the 90 just for the "double engine requirement factor" that I had on my .25 size Little Stick. LOL! What happens when you put a 10CC pipe on a 15cc motor? One thing I found very interesting when I was tuning the G-51 on my little stick was just bolting a header and pipe on the motor increased the RPMs by 1000. Tuning the pipe got me even more of course.

I've had such good luck with SuperTigre's that I'm probably going to stick with them for this project but that ASP has my interest as well as the TH 75. And with the Tower super saver discounts the Tower and SuperTigre engines can be had for a really good price. So keep the suggestions coming, all good info!

One other thing to consider is prop size on a .40 sized model. I think it is a given that I'll have to get some taller gear for the Ultra Stick (I had to make my own for the little stick) but I was wondering if a 75 or 90 size motor with a header and pipe will swing a 14x4W or 15x4W? I've had .40 sized engines all my R/C "career" so I'm venturing into new territory here. The 12.25x3.75 is a really sweet combo on the G-51, what would the sweet spot be fore a G-90?