Thanks for the feedback. Here's my thoughts on it all
I like the #5 as I feel it is very "contrasting" making it very "legal"
I also like the lettering up on the white because the boat tarp hangs low enough that it's on the blue, so it will be completely covered with the tarp. With the letters on the Blue area, the tarp straps might hit it while the shake around during towing, and maybe cause some premature peeling... But, what I don't like is that it really sticks out a lot, liek "DAYUM LOOK THAT BOAT SURE IS REGISTERED!"
On the flip side, I think when the numbers are in the blue area, it looks more subtle and clean. All the "colors" and pinstriping and all that stuff is all going on in the blue area, so it seems like it'd look the cleanest if it was down there where everything else is happening. But I feel like it'd be the hardest to make match the rest of the boat, while still being contrasting enough to never get hastled by the shore patrol. And also worried about the rubbing of the tarp straps might make it peel prematurely.
So yeah, I'm still kinda torn. I do however think I'm going to avoid 3 and 4 because I'm hearing from a lot of others that may be asking for extra attention from the shore patrol because it's not contrasting enough.