get a smaller rib
I would run the camera off the boat batt [minimal draw] and have it on a removable pole viewing at the same angle of the outboards - viewing from just above engine hood height mid mounted between the 2.
The most prone areas at the stern i would concentrate on getting a good view of
But it all depends on the angle the lens is some are wide some narrow - mine is narrow but it still shows up the entire 15ft boat and more
Best to have a play - set it up so its working and move it arround till you find the ideal position then think how you want it mounted
but the higher the better for me