If you're just doing 5x7", why not use a smaller tank for the developer (like 4 or 5 quart 5x7" tanks)? I do 5x7" in ABC pyro with tanks of this size, and I get consistent results with three batches of 8 sheets through the developer, one right after the next.
Michael Smith does 2 batches per tray of ABC, but I think tank development doesn't aerate the developer as much as shuffling in trays, and the volume of developer per sheet is greater, which is why I think I can get another batch out of it.