I've seen an airplane that size before. How much will it weigh? I would put something like 70 to 80 ounce servos on each control surface, except for 2 on the elevator. The 1/4 scale servos that most people sell are pretty slow, so they don't work as well . The Hitec 605 servos are great. I saw a 33% TOC plane with them, and it flew just as good as if it had $100 servos in them. I've also got the 605 on the tail rotor on my chopper, and it is great. Strong, and fast. It centers great if I unhook the gyro.

Now to the retract servo. You will probably have air retracts in this thing right? Well, once it is installed, see if you can get a standar servo in there. If not, a low profile one will work. Don't worry about a retract servo because all they do is move 180 degrees, which is just what a standard one will when it is hooked up to the retract channel.