Darryl Ramm wrote:

The boxes are sealed but the lower floor of the box usually is or
touches the bottom wing skin so if you really wanted to you could
drill a hole right there through the lower skin. Your A&P may have a
different idea.

But why? /snip/

Darryl

Drains are fitted to powered airframes because it takes relatively
little trapped water to give a very nasty aft pitching (or rolling)
moment...

Brian W