This is a situation I have disagreed with since I started in this hobby.
All of the manufacturers want you to build the plane and then install the insides and engine.
I prefer to get all of my gear possible in prior to mounting the tail feathers.
I do mount the engine and then remove it before the tail feathers go on. Now all of my holes are drilled and taped.
This way you won't bust anything off while moving it around to get everything to fit.
Granted, you may need to move some stuff for balance but if the servos and engine mount is installed these are the
hardest items and you don't usually move them around for balance.

This works for me anyways.
KW_Counter