Well, a couple reasons, actually. First, the spacers on the T&D shafts help locate the rockers, not just the hold downs. Second, I pre-machine the materials as much as possible to reduce manufacturing lead time. They are pretty labor intensive, so any changes from the norm is more expensive. And lastly, the roughly.060" shaft spacer thickness being transferred to the aluminum crescent spacer, has no effect on anything stability wise. Six of one, half dozen of another.