Does anyone know of an off-the-shelf solution to mount a camera upside down on a tripod, for the purposes of being able to compose with the attached LCD screen when using an M2?

Flipping came upside down will not help you compose. It will however make the camera record the correct image.

To see what I mean, flip the camera without an adapter. The image is oriented exactly the same.

However, flipping the camera, and using a magnet trick or lcd switch trick gives you the best setup because you see AND record the correct image.

As for off the shelf, I haven't seen anything. Dennis Wood (brevis creator) made an upside down mount as well as some other users on this forum.

duh...! Of course you're right, should think before I post....

Piece of 8mm x 40mm aluminium flatbar, threaded tripod hole for tripod, offset hole on one side for mounting TFT monitor rightway up with gutter screw, offset hole for mounting cam upside down on other side with gutter screw - works sort of but still very inconvenient.

You have to be very scrupulous and clean out the tape cassette enclosure to avoid any debris going into the tape cassetre when you capsize the camera.

Greg, our new rails system is designed to allow upside down mounts. For small cameras (like the GS400) they will do this out of the box, for bigger cams, you need to add a few of the standard blocks/risers in.