I never actually measured the end play. It was always just a feel thing to me. I would say it should be as close to none as you can manage. I always had a good selection of different thickness shims. Once I had the arm centered and shimmed on the bottom I would start shimming the top. Basically I would put them on and stick the hood on and spin it. If it was free and there was some gap I'd try to add a little more. If there seemed to be some drag on the arm I would try a different combination of thickness of shims in order to get rid of the drag while still being close to no end play. Trial and error and fiddly, but effective and I never damaged or burned up a motor.