[rthomas]

I have successfully processed 16mm short lengths in a normal metal tank. My method is to tape the 16mm film, emulsion side out, onto a previously-processed "junk" roll of 120 film. I tape both ends of the 16mm film down on the larger roll of 120, leaving only a little slack; obviously this is done in total darkness but it's not difficult. Then I load the 120 film onto a stainless-steel reel and put it in the tank. I process it as if it was a roll of 120. Uses a bit more chemistry that the 16mm film needs, but it works. I think you could do a couple 16mm rolls per 120 roll.

Now if my 16mm camera didn't have a dozen light-leaks, I'd be all set.

EDIT - I tried this trick by taping 16mm film to 35mm film and it did not work, the film was too close together.