I wanna pop a coupla holes on the bottom face of the trunk, like so:

Best I can tell, there's nothing behind it, ie just the sheet metal ... but my usual trick of reaching arms like a giant caliper around to check each side doesn't work as even my monkey arms don't reach.
Anyone who's cut into those, can you tell me if there's anything vital underneath to watch out for, or if a drill will just pop through into air?
(Yes, I know, waterproof it, etc etc, and yes, Ogre, I'm sure it's illegal in some jurisdictions and you don't like LED's.)
-- A