I've wondered that myself. With the snaps outside of the velcro strip, you can't leave the mattress snapped in place if you want to seal the tenting with the velcro. The only answer I've come up with is to unsnap when you set up, and resnap when time to fold back up. Unfortunately, that a recipe for wearing/tearing the snaps out.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller