Joe, Very sage advice on the use of those GPR sights, IMHO.
I do the very same thing to a "T", been doing that for many years, and it seems to work just fine. I have no desire whatsoever to change the sighting, or try something different.
(Did we ever discuss this in years past? Somehow seems we did.)
Bill, when you say; "The current flint seems to making good sparks, and drilling out and counter-sinking the touch hole bushing has made a world of difference in the speed of ignition. I also think I was over-filling the pan - it really seems to like 6 grains (2 pumps from my priming flask), which looks like way to little, but it goes off fast and reliably." ....Those two things right there, my friend, is a little something that many will go through life looking for, even after being told that it works, and works well for most folks....
You hang in there, you're well on your way to becoming a real "Rock Lock Addict".
Uncle Russ...