I am designing an enclosure that holds a lens (clearance fit) and a photodiode on a PCB. The alignment of the photodiode to the lens must be pretty tight, thus I am using a boss on the enclosure (also a clearance fit) to position the PCB so that the photodiode is directly underneath the lens. (see first image).
How do you address clearance fit gaps when doing tolerance loops? Is it good practice to shift everything to its worst case position when doing loops like so?: