sealing control surface
I guess I am cheap. I go to Wally-World and buy a roll of clear package tape. I take a piece and trim the width to what I need, then stick it on. Been doing this for several years and haven't had a problem with this yet.
Also, by keping the roll in my tool box, I have a way to patch minor holes and tears in the covering when out at the field and quickly get back in the air. For this application we call it "100 mile/hour tape" around here - sounds more high tech than package tape.