Holy smokes. I figured I'd get a slew of answers to this riddle.
I was thinking an old GS21 might make a good FE spec rigger but I wasn't sure if the newer GSX would be any better/different. I saw a GSX21 in the "for sale" section and I know where there's a GS that's in okay shape.
I would guess you did not get many answers due to fear of differing opinions. The SG runs cleaner and more free than the SGX. I recently purchased a .40 SG to repalace my .40 SGX.
Terry, it's difficult to apply logic to the Eagle's when converting to FE.
From what I know first hand they do not convert well if the FE system is all put in the front. This results in too much sponson weight. The best conversions or new FE Eagles run more tail weight and keep the sponson weight similar to a nitro boat. This usually means the motor needs to be placed further back than the stock nitro motor position.