I agree with kingwoodbarney, put the radio in last no matter what the instructions say. This is an especially good policy is you are using an engine larger than specified, which a lot of us do.

I normally install everything except the battery, rudder and elevator servos. Then I put the battery near the middle of the plane so I have some movement leeway later on. Then I rubber band in place the rudder and elevator servos and check the CG. If I am nose heavy, I move 1 servo to the rear. Still nose heavy, I move the other servo. Then I move the battery.

Installing servos in the rear fuselage is fairly easy. I normally just cut a hole, screw them in, remove the screws and treat the holes with thin CA and re-install the servo and hook up the pushrod. Normally, I can use a short piece of 2-56 or 4-40 rod for the pushrod. For rudder in the rear, I have been mounting on to- the fuselage and using short pull-pull lines to the rudder. You can also install the rudder servo on the bottom for pull-pull. Bottom would be better for an upright engine.

The most work I have had to do for rear mounted servos is to add in a little ply in one of the lightening holes for the mount. Usually the fuselage sides are 1/8 lite ply so I cut a small piece and back it on the inside with some 1/32 ply. You will need some servo extension leads.

Sure beats adding weight.