I have a 20x24 trimate processor, which is fine for FB. Processing FB up to 12x16 is easy with a single clip. For larger prints, I've made a jig onto which I slide a clip at each end, so that they are about 16 inches apart.
The hard part is dropping the prints into the companion Washmaster. Unlike the trimate processor, the prints love sticking to the glossy side of the slot. (Why, both sides aren't textured is a bit of a mystery.) When working on larger prints, I remove a divider to make a double-width slot, so that I can quickly drop in the print, and give it a quick wash before moving it to standard-width slot.
Two good ideas here. Andrew! Any chance of a photo of the jig?