Normally, I will build all the major structural components and then mount the engine, landing gear and fuel tank. At this point I will lightly tack on the tail feathers to get a basic idea of the weight and balance. I will also add the pushrods for the tail but will leave the servo ends unfinished and uncut. This does however allow you to account for their weight in the aft end of the aircraft when getting an estimate of the Center of Gravity.

CG considerations usually drive the location of the radio components as they are about the only weight that can be readily shifted in the plane to adjust the CG. At this point you can place the radio equip in the plane and adjust the CG. You may need a bit of nose or tail weight to adjust the CG even with the radio equip as far forward or aft as it will go. This is one reason I only tack the tail on as if tail weight is needed, I can add it in the rear fuse under the stab and take advantage of the long moment arm.

Once I have the radio equipment in the plane as well as any balance weight, I will finish the pushrods, cover the model, and then re-assemble everything and re-check the CG. I save the covering for last as it adds relatively little weight from a CG perspective but avoids dings and scuffs to the finish while installing radios, fuel tanks engines, etc. It's a personal choice though and you could cover the model first if you like.

In your case with a sheeted fuse, I would complete the sheeting before installing radios etc, as it adds a significant amount of weight to the tail and you will still need pushrod exits etc. As long as there are cutouts in the fuselage formers for the pushrods to pass through, installing them later is not a problem.