I'm waiting for it to happen. In fact we talk about almost jokingly now ever time we go out to surf. I don't know why it hasn't happened yet, but we've never been stopped while loaded up with ballast. When we are surfing, we have water splashing over the rear of the sundeck on the port side, when we are sitting the rubrail is a good inch underwater. We normally only have 4 to 5 of us onboard at once anyways, so I think that helps with not getting messed with as much. We are always a good 500 lbs or so just in ballast, not including the gear, crew and ice chest. I'm sure we'll turn the corner one day and find a cop sitting there waiting to nail someone and we'll get our tickets.
As for not having a plate, I'd be surprised if there wasn't one somewhere. I've seen them on big 30' plus fishing boats before. We're in a 21' Wakesetter and it has a plate, but its also an older bu.