Joe:

The flapper valves are internal to the Bosworth pump. I'm not sure there are any options for the material for the valve. Give Bosworth a call, they are very helpful.

I don't know if it's worth the plumbing and aggravation to try to set up a system that will pump out both your forward compartment and your cockpit, but it's certainly possible. I'm inclined to keep things simple, and easily taken apart for cleaning (though the Bosworth seems to be very robust and able to swallow most of the junk you might get in your boat).

It's possible to set up a footrest/pump bar across the width of the kayak by attaching a strip of material to the button of the Bosworth pump. This would make it similar to the Henderson pump installations found on British sea kayaks such as the Valley Canoe Products Pintail imported by Great River Outfitters. I've tried one of these, and they work well, though it might be difficult to adjust the position of the foot support. With both feet on the bar, they are solid enough for rolling and bracing, and the pump is easily actuated by the bar.

Jim