You can get 6 or 8 racks in an MES 40 easy. Just take and make a circle like you see a crown rib rack done. You can tie it with binding twine or skewer the two ends together. Cooks the same, will relax flat when you get ready to foil. I can easily get 4 rack in my MES30.
Really no problem, I assume you could just leave 'em circled up for the whole cook if you were doing 'em old style.