Derek,
I had a blank cover over the drive mechanism, but pulled the drive/spacer mechanism off at the last annual. I then also pulled the studs (which were protruding) and replaced them with bolts (note these are coarse-thread bolts - I used 1/4" #8Hard bolts from Lowes since I couldn't find official AN bolts of this configuration, and drilled the heads myself for safety wire) when I put the cover back on. If I had not had the cover, I would have made my own from a piece of 1/4" plate. Saved me carrying around an extra pound or so on the engine (now, where did I put that big bowl of ice cream???).
cheers,
greg