I agree with CGr on the hinge sealing issue

IMO for most sport fliers and trainers sealing the hinge lines is over rated providing the initial hinging was done correctly and there is little to no gap. I will also seal hinge lines as a corrective action on students airplanes where the gaps are too wide but not bad enough the re-hinge the control surface. I generally seal the hinge lines on my pattern birds as a matter of course when assembling or covering the airplane.