Hi John,
I have no notion of the feasibility or advisability of what I am thinking, but here it is. Take a removable boom vang setup (something like this)
http://mauriprosailing.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GAH30US41&Category_Code=GARBV
Shackle this to your traveler pendant on the aft deck. I've seen the floating traveler setup, but not sure what hardware you would need to do it. Also not sure if it needs to be adjustable and cleated, or if a fixed line with a block on it will work. The downside is you will have to be at the aft of the boat all the time. Hope my idea helps some.
P.S. I would install heavy reinforcing plates under the attachment points on the aft deck (as large as you can fit under there). Some of the more experienced people here can advise you on the best type (wood or foam glassed in vs. metal). That is a lot of load in a weak area.