RE: Viper Thottle Servo Placement
I moved the normal throttle servo tray back a bit in the fuse to clear my tank (Jett 6oz slim). I went ahead and did this (although I shortened the tray a bit) to provide structural strength in the forward fuse area. I then mounted my throttle servo just aft of that. I used a couple of short basswood rails to mount my servo on. You need to watch and make sure that your aileron servo clears the throttle servo.
I use JR MN48 servos in the back, a HS225 for the throttle, a 270 mah nicad pack, and a 7 channel Airtronics rx. I put the battery and rx in the main fuse compartment (under the wing) and had the balance come out perfectly. Weight was exactly 3 lbs 12oz.