The "Max Speed" thing is a load of shit. As in... not a real law. I've been on boats, and Water craft all my life... and I've never heard that. Heck... I've even had my PWC go though the USCG tests, and they never said anything about a speed rating. The reason I know that one is a load... is that you don't have to wear your life jacket while underway. (aside of local laws) SO... if you are going 55 mph... and have an issue... how are you supposed to get your life jacket on while being thrown from the boat? (Hopefully we don't have to find out)
The hull number thing I understand. To them... it has to be in the right spot, and the right size... and the right font. Depending on the hull... it doesn't always work. Heck... on the new Spark, you can't put them where the USCG wants them. But, here again... depends on the person doing the inspection I guess. My old stand up skis... I put the numbers on the rear of the craft. (by the footwell) The only time I got hassled for that (during an inspection) was the font I used on my last XP project. I liked the look... but I even admitted that it was hard to make out the numbers. But, in the end... they allowed it.
******EDIT******
I just was on the USCG's web site. They don't not even recognize a speed rating. Just the type/style for different applications and body types.