robert, I use a Paterson orbital processor in whch you can develop 4 off 5x4 negs at one time or 1 off 10"x8" neg.
the tray consists of a bottom half with peg holes to seperate it into four sections, the top half is a light proof lid with inlets and outlets for filling and draining.
the tray sits on a dome which when switched on rotates and tilts the tray for the process times, after loading the film the process is carried out in daylight.
I bought the unit about 15 years ago for developing 10x8 cibachromes and only recently used it with 5x4 negs all of which have been ok.
I dont know if you can still buy them new but I have seen them on UK ebay.
I hope this helps.