Ford has changed the design on their soft snapless tonneau covers. The cover I reciently purchased for my '03 Flareside uses a 2 stage locking design on the railing, different than the one I had on my '00. The cover locks down tight & there is no chance of the corners curling up. On the down side(IMO) is that the cover is only available in black. The dark grey(which matched the trim) is no longer offered

 

Just another vote for the Sportmasters tonneau. It went on without headaches, is virtually watertight, and was easy on the pocketbook (around $185). It's also all black (i.e. rails, bows, snaps, and cover). Before I got the Sportmasters, I installed an Extang Black Max cover. It fit soooooo poorly, I immediately removed it and sent it back to Extang. I didn't go for the Ford OEM tonneau, because I have yet to find one that the corners didn't curl on.

I don't think you can go wrong with the Sportmasters.