Mine were on the hod when I rode at Grapevine lake and I never had a problem. Even rode out at Lewisville and no one said a thing to me...
Like I said, I've never seen anyone get a ticket for having them on the hood or pole, but I have seen the watercops mention that it's not legal, mention not very legible, etc. The cops at Lewisville are usually very decent with us since they've long since realized we're pretty harmless and pretty careful. They usually don't even safety check us anymore (used to be an annual thing, often on the first or second ride of the season so you're floating in COLD water while you try to get your fire extinguisher out).
We've also worked pretty hard at being friendly, we offer water, hotdogs or whatever if we're grilling, and we pick up our own and everybody else's trash at our ride spot. A little schmoozin' does wonders for how much the law will ignore. Christopher's little girl was seen riding around the cove at 9 yrs old (way too young to even get a boater safety cert.) and the water cops just said, "You really shouldn't do that" and left it at that.
So, stunt318, that may be why you didn't get questioned, you were with our group and our trained water cops at Lewsville. Grapevine cops are somewhat trained, but mostly get drinkers and idiots. The ones we ran into were always pretty decent once we chatted a while (if they came by at all).