Charles:
I tried a couple of different types. I originally tried some self-stick neoprene weatherstripping (1/4" x 3/4"), but it did not compress and the hatch sat too proud. I am currently trying a self-stick neoprene stripping that looks like a "D" lying flat. It is hollow in the middle and compresses well. The seal has been good and the material is cheap and available (I got mine at HD). It comes in a roll with two strips connected (a double "D"). I found it easier to separate the strips and mount them with a small gap between them.

Regards,

Marcel