Yep... what Andy said. I have no trouble raising the hose to dump air to start my descent, but I actually end up primarily using the rear dump valve during the dive.H2Andy:if you only put your inflator hose (but not the corrugated inflator itself) through the d-ring, it's a lot easier to vent.
As for where to get the bungie... REI has it here on the west coast. Someone mentioned Walmart. Any major fabric store should have it as well. Most of these places sell it by the foot.
Here's a pic of how mine is set up:
