Bob, you know it did not dawn on me until now that he wants this for a 35mm camera, I was thinking more of a studio set up. What my friend did was to use clamps to hold the set up on a light stand. I think balint plans to use slaves and the flashes off camera so I would think this still applies.
The boxes were actually lighter than any soft box I ever saw or held.
Sorry but no plans, at least that I know of, but maybe a google search would find you some.