A 4" dredger typically has a 3 1/8" nozzle. They want a 3" nozzle. I put a 1/8" reducer in mine so ir is 3" exactly. I've never seen them actually measure anyone. Last year they "would like" you to have a permit. I didn't have one but when they came by, I filled it out and gave it to them. I don't know what they are doing this year. I'll probably try to get one in advance.
Leonard