Well, two updates on my progress -
I tried making my own ULF insert for the 3063 - that was not a failure, but less than 100% successful. No rib lines, but frequent lack of clearing of the anti-halation layer in blotchy patches, of course in the location most likely to ruin the image. Someone over on LF Info suggested another option, which works. Take some of the open-cell foam weatherstripping you can get at Home Depot (1" wide, 1/4" thick) and cut it into little squares. Attach the squares to the sides of the drum at the approximate height of the sheet of film, and again at the bottom of the barrel. Developer flows around and through the foam, so you get even development, and your pre-rinse likewise, so all the anti-halation coating comes off. I'd do trays to do more than one sheet at a time, but I always end up scratching film when I try souping in trays. I'd rather take more time in the darkroom souping one sheet at a time than scratching film that I can't easily re-shoot, at $12/sheet.