I re-built a Pacific K2 'no-drill' peep sight today by combining parts of two incomplete sights.  In experimenting and trying the K2 on a Krag, I discovered this particular K2, at least, requires no 'notching' of the issue stock to fully function.  The two Pacific K1 sights, I have, require a small notch in the stock for the elevation slide to be fully lowered.  (The slides could be altered by removing metal to eliminate contact with an issue stock).