Oh, you ARE in California. I'm very interested in hearing how your registration process goes. I've researched California SPCN for motorcycles, but it'll be great to hear about someone going through the process with a homebuilt EV trike.
If you're in Southern California, you might want to check out the Alt Car Expo in Santa Monica on September 30 or October 1. I've been two or three times. I sat in a BugE and saw Jory Squibb's Moonbeam and a Corbin Sparrow among other interesting vehicles. It seems to be moving away from DIY toward corporate, but there's usually some pretty cool stuff going on, and admission is free.http://altcarexpo.com/
Personally, I would avoid putting so much weight on the rear. I'd worry about tipping while swerving to avoid something. Check out how easily this Messerschmitt reverse trike tips!http://www.youtube.com/watch?v=InlFaERcPeA