Yep, mine was mounted like that too..... Amusingly the sealing was done by parking an offcut of rubbing strake between the hull & the stainless plate, and as it was primarily there as a lifting eye and not to hold the frame down, I had 4X 20 odd mm of M10 thread and a nut poking down below the hull from the U- bolt. Made it an @rse to get off the trailer!
I decided to streamline it a bit on the assumption the boat is no longer in a commercial role so no need for the lifting points, and replaced it with a gallon of sikaflex, a few pan head screws and a couple of eye nuts inside to keep the lash down option available.
One thing to watch - keep an eye on the leading edge of the plate - it;s amazing how quickly the sikaflex is jetwashed out by the passing water.
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