Before I go on, please note that I'm brand spanking new to all of this about motorized bicycles.
As I mentioned in another post, I'm considering moving to Puerto Rico and am thinking about building one of these for use in and around the little town where I'll most likely be living.
I don't know what the current laws about motor assited bikes are on the island. All I could find are Moped laws. I'm familiar with those because I had one years ago and shipped it to Puerto Rico. I had a **** of a time because, even though it was under 50 cc and had pedals. They wanted me to register it as a motorcycle, but since I didn't have a Title of Ownership (I bought it as a bicycle in Newport, Rhode Island), I had to hire a lawyer to prove I was the owner, etc.
Anyway, I'm fascinated anf enthused by the idea of doing one of these builds.