I used Taco 5/8" neoprene weather seal. They have it in 10' rolls at West Marine
http://ecatalog.westmarine.com/full....ckProdId=36410
This weather seal has an adhesive backing, but it doesn't stick to the hatch material very well. A little Goop will help keep it in place.
I get a lot less water coming through the hatch with this arrangement.