Use the magnets.

Recess the magnets into a support frame for the hatch and CA in place, then cut some STEEL strips about 1/4" wide by about 3/4" long and CA them in position on the hatch cover. Be sure the hatch cover is flush or SLIGHTLY below the rest of the fuselage, then cover the hatch cover.

I have not had any problems with magnet held hatch covers. I have a couple of glow planes that easily hit 90 mph. I have a hatch on one of them that is 3 1/2" wide and almost 6" long. That one has 6 1/8" rare earth magnets on it and never come loose. I even had a landing that ripped out the gear and all it did was shift the hatch.