I've seen photos of that done. Looked OK but I think I'd prefer to connect on a less destructive way. I'm planning to make solid copper tabs rather than a PCB to connect mine (when I finally get round to it).
I'll be interested to hear how you get on with insurance. I suspect anything home-made (no matter how well done) will be difficult and expensive to insure.
That site used to list Zero motorcycles for sale but I'm not sure they were ever a dealer. Sounds very fishy. Almost tempted to sign up for a free test ride, but I suspect that would never happen.