: . . .A haul system for moving inflatable bags in and out is starting to sound good
: to me. No skin on the boat yet, so I'm not too late for that detail.

Secure the haul system with a big knot somewhere in the line so that the float bags won't float away should they come out of the boat. Sometimes that happens.

If you are making your own vinyl or PVC float bags (see Tom Yost's ideas at www.yostwerks.com) you don;t really need any valves. Just glue in a long vinyl tube, and cap it with a tapered plug made from a conical block of wood painted with a bit of epoxy resin. Use a folding top to mostly fill (or empty) the bag, then top it off by blowing into the tube.

clear vinyl from WalMart's sewing department is inexpensive and works well for this. A tube of VLP is a good adhesive for gluing the few seams you'll have on a couple of float bags. You can find this at many craft stores and hardware stores for about $3. Below is a link to one supplier's web page.

Hope this helps

PGJ