Ihave several planes that have "holes" in the control surfaces, one is a SIGSomethin' Extra with laser cut holes and the other is a Hog Bipe with self inflicted "circle cut saw"holes. Both are afflicted with noticeable sagging covering over the holes. Both are kits built by me. Both have their hinge gaps sealed on both sides. Both are covered with Ultracote. I have used a heat gun and hot iron trying to eliminate the unsightly sag (the plane!not me). With each tool the covering billows up as there is nowhere of the expanding air to escape. Oh, during the original build of each, 1/16" holes were drilled in the LE of control surfaces into these cavities - worked for the inital covering but not for shrinking after the hinge gaps were sealed.

My question: How do you address providing venting for these areas?

TIAfor sharing your experiences.