I finally got a chance to get this in the water and wanted to update the thread. It worked great! My balance/trim was almost dead neutral. About 2-4 lbs. is all I needed to get negative. The unit rode nice and tight against my back without lifting like a stock Dolphin, and I don't even have a crotch strap. I was able to roll over and invert with little difference in WOB. It's a little bulky on the shore, but once it's in the water it's very comfortable. All in all I'm very pleased with my project. Thanks for all the help and interest in my new toy. FD
(I tried to include a pic but it wouldn't upload. Not sure why.)