I tried this once as well, to no end.
I have, however, come upon a way to increase my processing capacity for 5x7 negatives. Pick up an expert series 3005 Jobo tank. It's the tank that allows you process 5 8x10 negatives or prints at one time. In the darkroom, pair up the exposed negatives, connecting each pair with a cellophane tape hinge on the back of the sheet along the 7-inch side, creating a 7x10 inch sheet. Put the joined negatives into the tank as you would single 8x10 sheets. You can process 10 5x7s at a time this way.
The only downside to doing this is that the tape traps the antihalation dyes underneath it. But with my TXP, at least, it comes out in the wash after 40 minutes or so.
Sanders