I don't know about the MP distributor but I've run into a couple stock ones that as the vacuum advance moved the pickup plate, the gap decreased. I had one where the gap decreased to the point the reluctor contacted the pickup.
years ago one of our members from south america (Nacho) did something to his advance plate to where he got the change down to several thou iirc to resolve that. not sure what he did but you might eyeball it & see if anything jumps out at you that you might alter that will decrease the change.. EDIT I am thinking that he just relocated the pivot point so there was less arc in the sweep
