I have a few 7" and one 9". Whatever you do, don't slice open the bottom. That defeats the purpose of rerigging it so that it won't rip open. Just pull the harness out. I don't know how much it weighs. The Osprey sinks really slowly, and perfectly level, but you might have to add a mojo weight to the belly when you re-rig it to make it run straight.
-Brian