Leegscott, you know, there might be a way to mount the tanks side by side. If you can widen the opening in the bulkhead to accept two tanks on a plate that would be removable. Hum! only a thought! At least you can mount them both on the C/G. I guess it depends on how big the tanks are.
You have to be careful of an airplane that is naturally nose heavy, i.e. smoke oil on board all the time, because if you have to pull a lot of elevator too low too slow, it will snap.
The dual elevator servos are a good idea. Be sure and build a sub-C 6 volt pack so you have all the ounces and speed the servo will deliver.
Thanx for the complement on the full size project. I'm affraid I won't be the pilot. Hank my friend is. I will be on board though you can bet. bird.