My worm and worm gears came in yesterday. If I use the "double-worm-gear" arrangement I'd planned, there won't be enough clearance between shafts to mount the pulleys to drive the saw belts. Grrr.
I might be able to offset the pulleys such that one is higher than the other, but I doubt it. Another possibility is to have one pulley above the worm gears and another below them. That will make for a tall robot.
File this one under He-was-too-clever-by-half.