from the limited amount of tray developing that I've done in 4x5 and 8x10, I've always found glass baking pans to be the best. every time I've used plastic trays(even the ones with gulleys on the bottom), I've gotten scratches. with the glass dishes(approx 2-3" deep) I've never gotten scratches of any sort whatsoever.

I've been searching for a large glass dish that can handle negs of this size, but so far no luck.

Otherwise, there are plenty of people on here that use a jobo system for ULF development. I would imagine that you could use a large print drum(without ridges seems to be best from most people's accounts), and use it even in a water bath, rotating by hand.

best of luck though.