Actually, the gaskets are supposed to stack up until there's a slight clearance between the bell and the cover. It's not uncommon to have to use more than one, kind of like setting the worm gear bearing preload on a steering gear by adding or removing a series of thin gaskets. The side clearance on Ford banjo housing rear axles are set the same way, with single gaskets of variable thickness. If you need to add more gaskets, you don't have to pull the torque tube again. Just make a diagonal cut at the top of the gasket, slip it over the bell, and dab a bit of #2 Permatex at the cut site for sealing.
Jerry
