I would set it to "average out" with change in vacuum so that let's say, no less than .005 or so at absolute closest point. Take shaft wobble / wear into account. I assume you have a handy "hand" vacuum pump?
Just got done adjusting it one last time. I replaced the pick-up with a better one from another distributor I had and adjusted the gap to .010" with no vacuum and .005" w/ vacuum applied. I used a mity-vac hand pump for vacuum.
Between fixing the huge reluctor gap and reluctor wheel phasing issue, we'll see what happens...
One last question... Do you guys drive the reluctor wheel roll pin all the down until it seats against the bottom of the groove on the shaft? Or half-way? All the way down doesn't seem to leave much left to 'grab' the reluctor wheel.