I'm not sure how doing it in a tray would be (shouldn't be too hard to retard the slight temperature drop 3:15 would incur), but I've been doing a lot of 4x5 with the powder press kit "taco" style in a Paterson tank. The only problems I've had were my own fault from not agitating vigorously enough in the beginning. You may think it crazy, but it was actually the first film developing I'd ever done (have yet to develop any B&W).

So far, I've processed 32 sheets of 4x5 and 7 rolls of 120 since I first mixed it in November. That's almost twice the stated capacity; not sure how much further I want to push it.