I designed and printed the final piece to my PGP2 project. With my feed cap, plug and Cocker frame adapter all reprinted in PETG, I created a replacement sight rail that snaps on without any permanent modification to the PGP2. This sight rail is perfectly centered by using the slot for the speed feed as an anchor point. Once snapped into place, the sight does not move.
As usual, the model has been uploaded to Thingiverse