Something I am working for Mr Ploffy - Tortoise motor covers. We are in the testing phase at the moment but I thought they might be of interest, as they could be used indoor to protect the units under a baseboard.
Ians units will be in perspex and glued to form a water resistant unit, these prototypes are mdf
The concept is dead simple, a pre drilled mounting plate with a cover, these are destined to sit above the board so the cover fits over the mounting plate so the water drains to the surrounding area
the view from beneath, but obviously it could be adapted to work upside down
These will need some wiring holes and grommets, plus some feet to raise them off the deck, but this piece can be hacked to test all that out