RE: Tuning the Single Cam?
It's not just for speed/efficiency.
Any time you rotate that cam out of it's optimum position you affect where the nocking point on your string comes back to rest when fired.
You are affecting the nock travel. If you put the string on a different post, yest it should return to the same position evertime (assuming no string/cable creep) but you have already put the arrow flight in a less stable situation (either causing the nock point to be higher or lower than normal), hence the reason onecams are generally either a breeze, or a complete bitch to tune.
Good bushings and a perfectly round idler are crucial too, as this will again, affect where the nocking point returns to after every shot. You'd be surprised how this can affect the accuracy of a onecam bow; it totally ruins consistency from shot to shot.
JeffB