I have a Balmar and a Motorola alternator. The standard A4 belt that the Motorola uses is too short for the Balmar and the next bigger one is kind of loose even at full adjustment
I was getting annoyed by this and decided to really cram the short one on. I managed to get it halfway on and it was stuck. Not coming on or off
It was fully on the alternator and half on the engine pulley. The part that was on was towards the outside of the engine. I decided that I would crank the engine to get the belt to pop off and go to plan B. Well to my happy surprise it went right ON instead and once in the pulley has about 1/2" slack if you press on it
So far working great and no slipping.