FlyNavy, I'm considering the same thing for my tub. I figure I can run the spin pole downhaul forward, through a block in front of the forestay and use that as an adjustable tack line. Use the spin halyard as, well, the spin halyard and then run the sheets. Outside gybing it should remove any problems around the sail getting stuck between the luff and the forestay, means longer sheets but no biggie and that's a ton cheaper than trying to add a sprit.
I was going to try it out by flying my symm as an asymm, yeah I know, lousy sail shape but just to prove the rigging it will work.