I see there that you made a splint for the cross bar, a constant reminder of your brain fart <img src="/forums/images/graemlins/notooth.gif" alt="" />!!

As far as that flap goes you could always put like four snaps to keep it from flapping, its not like it would be much work now that you have all the tools.

Or if you really want to owe your mom have her sew two high quality zippers to the fabric. Put Both zippers on the flap and than the side of the track on the top and other on the bottom piece so when you run just the top its comepletly removeable, or on that note one zipper on the top of the flap and sew the other side to the bottom cover. If you get a good quality zipper they are water proof and pretty heavy duty for pretty cheap.