I've heard stories of some producers putting mics inside flight cases
effectively using them the same way a speaker uses an enclosure. Do many of
you use this technique? I tried it recently when I was trying to get a
Queens of the Stone Age type bass sound for a band using a Big Muff pedal. I
had a clean DI going to tape, a distorted amp sound in the room and tried an
MD421 in a flight case nearby.

The flight case resonated at certain frequencies which is to be expected. I
compressed this mic hard and when I mixed the 3 tracks together it did
indeed add to the ROCK! It added mostly in the upper harmonics of the bass
and I guess this depends a lot on the flight case.

How common is this practice?

Any producers here care to divulge any wierd and wonderfull tricks to try.
After all, thats what we're here in R.A.P. for!

Martin