Another way that would work (and close to what I'll wind up doing if/when I ever print larger than 8x10) is to one-shot everything and develop in a single 16x20 tray. Set up with your presoak already in the tray, developer and fixer (no stop bath needed in this case) mixed and in graduates before you turn out the light. Soak the film, pour off the presoak, pour in developer, develop, pour off developer and pour in fixer, and after one minute in the fixer you can turn on the lights to see how big a mess you made pouring out the presoak and developer. Rapid fixer that normally dilutes 1+4 for film or 1+9 for paper will do a fine job on a one-shot basis at 1+24, possibly even greater dilution (I'd be tempted to try 1+49 for a one-shot application). Expect fixing times about 3-4 times as long as you'd normally give for film strength, but if you turn on the lights with the film in the fixer, you can see when it clears; fix for twice that long (shouldn't take as much as ten minutes in the fixer in any case).