To pinpoint location for control horns and servo mounting, I cut wood screw tips and mount them in mounting holes, then press bottom sheeting down gently to mark the cut-out locations
I use T-pins to line up the wing sheeting before applying CA
Sheeting is simple after all the work I did and the ribs, etc, to make them perfect gluing contacts. Having servos, control horns and gear completed prior to sheeting makes both the sheeting and the hardware installation faster and more accurate