Roger:
I went with the supplied fuel tank & installed a gas stopper, works great & the G-62 will run about 15 minutes on a full tank, I then installed a 24 oz dubro tank behind the fuel tank for smoke oil & a tme smoke system, as for the ailerons I used four 110oz/in servos But I haven't heard where anyone was having problems with two. I think you need more power in the elevator & rudder than what you are planning. I used two 110 oz/in servos on the elevator & two of the same on the rudder. What I have is probably a lot of overkill But the way I fell more power is better & "I would never fly a plane this size with anything but metal gear servo's" Had some bad wrecks thanks to plastic gear servo's, they are alright for 40-120 size airplanes but not for large/powerful planes if you plan on keeping it for a while that is. If you are going to use a computer radio I wouldn't use a y-harness on the ailerons, I would split them so you can program in flaperons/spoilerons & all the other cool things that they will do. As far as the receiver I installed mine in the recommended place which is under the cockpit floor. You will see a plastic tube from there to the tail of the plane & that is for the antenna, works great. It should show this in the instructions It also shows a receiver box that can be purchased from tower hobbies but you can build one very easy from balsa or light ply. On the engine box depending on which engine you are going to use you may want to do a little more than just two pin's on the sides. I tried this & after the fifth flight the firewall was loose, I then pinned the top & bottom, put tri stock inside the engine box behind the firewall & glassed the entire engine box. Depending on the weight of the plane you may need to do a little beef up on the landing gear. My plane comes in @ 21# full of fuel & smoke oil & a slightly hard landing will spread the landing gear very easily.
Sorry for babbling, I hope this helps
Good luck
Gil