The second-most important item in the design is the tarp. Heck, I live in Florida; we get six months of 3:00 PM thunderstorms like clockwork.
So, I've come up with the following design:
It's an hex tarp that measures 12' 6" long by 10' wide. With the 1' 6" head slit at the middle, that should allow it to fold up to the dimensions of a standard USGI poncho.
At each corner of the tarp, I intend upon placing a mitten hook attached to grosgrain or gutted paracord loops. This will allow the tarp to attach easily to a separate CRL to be strung up before taking the poncho off. In addition, I can carry stakes with the lines already attached to clip the tarp to. This should minimize my time in the rain without a poncho and offer a semi-sheltered place to hang the hammock.
When wearing the tarp as a poncho, the mitten hooks will clip to loops attached to the head slit and to a pair of loops centered at the point where the hex cuts begin. This will pull the tarp in far enough to keep it from being too unwieldy, at least in theory.
My issues are as follows: the poncho/tarp is going to be heavy and bulky compared to a normal poncho, it is going to allow me to get wet setting it up, and it does not offer any end protection against wind-blown rain.
We'll see if this winds up being a valued piece of gear that helps lower my pack weight or a white elephant that I wind up hating in the field...