macro-RCU I'm only thinking very little here and hardly enough to change the flying characteristics. The thing is, it can be very disappointing having to add weight later. This plane was designed with two servos in the stab and should balance right that way. I will be using one servo mounted in the fuselage. The stab, fin and rudder will be covered with paper which weights only 1/3 of the veneer I used on my previous T2K. Of course you are right about changing moments, CG, etc but I think it's best to leave that to designers.
In the 2 meter plans thread there was an excellent T2K built by Bokuda with the elevator servo mounted in the fuselage which needed weight in the tail. It would be best for my to contact him to know how much the CG changed.

Wladimir I'm using 7mm thick, on the bottom piece it did taper down to 5mm.