Peter first mentioned this modification & I suspect that it may be one that he & his contemporaries used, but by no means all armourers. I haven't seen any T's with this mod but I have seen one or two L42's. I have modified a few L42 sights myself over the years. If you have the facilities you'd mill the underside of the cursor so as to give clearance, but you can do it with a half round file if you are careful. Of course, the cursor will then need refinishing after, ideally by bead blasting, parkerising, & suncoriting.