Parallel Entry Principle

I am trying to get information on roll dynamics and what I believe is called the parallel entry principle. My problem is I have a manufacturing process that uses many different sized drums or rolls that the processed product must travel through in order to become the finished good. I am convinced that any minor change in placement of a new drum when the old drum wears out will cause an upset condition, crease in the processed good, or cause a tension issue. I remember an article on what I believe the author called the parallel entry principle that could back my case for a new piece of alignment gear.

Any help would be appreciated.