I have a pilothouse mono and have consider this on the pilothouse roof to carry light stuff like fenders, boat hooks and other stuff that would go into the cockpit
lockers I do not have. It might be a solution for a valise-style liferaft
stowage, although most most that next to the mast
or onto aft stanchions.
I would have questions about their durability and ability to resist corrosion
, shearing forces and occasional wave whack. Clearly, they can resist highway speeds, but few cars are sideswiped by rogue waves.
So while I wouldn't reject the idea outright, I would question whether it is practical. Perhaps it is on a cat...you'd want to paint
it a lighter colour, however!