If you like the Z I'd take a good look at the 16 foot version. It has more knee room with a bit higher deck and the same performance as the 15.5. The other option is to remove the thigh pads and replace them with some 1/2" thick neoprene or minicell foam. This opens up some room, as well. Lastly sometimes moving the seat aft a touch helps reposition your legs/ thighs.

BTW- I work for Confluence Watersports (who makes the Z)and helped design it along with Bob Mc Donough.

Steve Scherrer