You should probably do what most velonauts do and get a laminated copy of the vehicle code showing that your vehicle is considered a bicycle. Next time you get stopped, whip it out. Maybe mount a video camera to the bike to record encounters as others have done. The one time I was pulled over the officer tried to tell me I was unsafe because I didn't have standard car equipment like mirrors and lights as I pointed out each one of them along with the six large red reflectors on the sides. Then she said that if my velo wasn't so bright that drivers wouldn't be able to see me. I told her "well, now you know why it's so bright". She was actually reasonably polite once she realized that I was complying with the law and that she wasn't aware of it because she had never seen a velomobile before. I tried to get her to sit in it but she wasn't having any of that.
JJ