: Good thinking. I tested a similar rolled up skin closure a few years ago,
: but found mine to be a bit awkward to roll up over such a long span, plus
: a little bulky. However, it would certainly be waterproof, just like
: on the dry bags you mention. I may give it a second look, as at the time,
: I wasn't looking for waterproof as much as I wanted it to look good.

Tom,

I'm sure you have some scrap material you can experiment with. Play with the shape of the flexible batten which the material will fold over to get a size that makes it simpler to roll. For an 8-foot-long closure you might want something two or even three inches wide. Or, maybe you need to bond three thin battens to the flap material, with space between them for the fabric to fold. The battens would force the fabric to fold in the correct place, and keep the fold even along the length of the seal.

You could make open ended pockets the length of your seal (8 feet long) and slightly wider than the battens, and slide your battens into these. Should a batten break yo pull out the pieces and replace it.

However wide you go with the batten(s) will determine how wide you make the flap opening and how much fabric you need for the flap so that it can fold securely.

Good luck with this.