ORIGINAL: Gray Beard

Before I hard mount anything in a build I finish the plane, install the servos, controls and engine/motor. Everything that has a place it must go. Then while still in the bones I set the plane on the CG machine and use tape to hold the parts like your battery in different places to get the planes CG. Then once I get that I hard mount the parts inside the plane then cover it. Most of my builds are ready to fly while still in the bones. I have even set up the controls in several of them. I do this before covering so I can get my fingers into those tight places and changes can be made.
Just something to think about at this point. If the servos and controls aren't in the way I leave them in while covering. Once CGed there is no reason to remove them.