Patriot,
You could go ahead and build the servo pockets in the tail and then cover over them with the fabric. Id the plane won't balance you can simply cut the covering out of the pocket and mount one or both of them later. It would be a LOT easier to do it now and have it available should you need it as opposed to ripping a bunch of covering off later and having to redo it after building the pockets in at a later time.