I haven't seen anybody else talk about this, and I have yet to build a prototype. My idea was to utilize a passive system to grab the totes, and to do this, grab from the handles on the shorter sides. In short imagine putting a piece of wood up into the handle, this piece also runs along to almost the bottom for support. Basically it relies on the bottom brace to keep it upright while the lip holds the inside of the lid. Here is a link to some quick sketches I drew.
https://www.facebook.com/photo.php?f... 571615&type=1