I just made a sight like that for my .58 English long rifle. I used one of Tom Snyder's drill guides to drill the hole through both sides and drilled the blade separately. That guide is a fantastic tool....Taylor, the spring is a stroke of genius!! I have been trying to figure out how to get the leaf to stay up reliably...... I learned a lot. Thinking through and filing the right tolerances ............. well as I said, I learned a lot!!