I have a slight quandary right now. I want to buy a bellows set with slide copier to copy some colour slides I have onto B&W film (in order to print on paper).

I'm using a Spotmatic, and my macro lens is the SMC Macro-Takumar 50mm f/4, but I can't figure out whether I should get the Bellows II unit or the Auto Bellows unit. The only thing I can see that distinguish them is that the Auto bellows can close auto diaphragm lenses, while the II has two tracks instead of one.

Does it matter at all? Also, I've read somewhere that the extra pin of the SMC lens could cause some troubles on certain bellows. Any knowledge of this?