N1EDM, thanks for the reply and info.
I'm not real concerned about room for the tank, the gas engines need much less gas to fly the same amount of time as the same size glow engines so a smaller tank could be used if needed for the same flight time. Another thing to remember is gas engines have pump carbs and don't require the tank to be mounted next to the firewall which allows the tank to be mounted on the CG point of the plane so your trims don't need to be adjusted as your fuel is used through out the flight.
I don't plan to fly this plane fast but I do plan to use it as a fun to fly daily flyer and I don't want to have to keep the throttle 80-90% wide open to get good performance out of the plane. I'm looking for an engine that will allow normal loops and rolls at 50-60% full throttle so there's some throttle left to use when it's needed.