Hi Trent
I was thinking about two OS-55ax engines or two OS-60fx probably i will go with the 60fx, it states not to go any higher then a 60 sized engine or i would of gone with a os-90 two stroke, with a little suort i think that it would handle the 90 size engine, i have not checked the weight out yet but i bet there isnt much of a difference and you can always put the battery in the back near the tail, i have a jr sport 2700 size battery in my c-160, it is in the front but is a heavy battery and could go in the back if need be. rollie