Thank you Rich for that post. I am thinking it took considerable time and effort and I want you to know it was both appreciated and useful. I took the bait and went through RCA I and II and Longrifle Articles I and II in search of scalable photos of the muzzle. Excluding European guns, there was a grand total of six. Eliminating the one that appears to have a web almost 1/4" thick and assuming a muzzle measuring 7/8" across the flats, the average web thickness appears to be a little over 5/32". Also eliminating the rifle with a substantially thinner web, the average web thickness increases to a little under 3/16". I think the latter is the best average, and both correlate very well with Rich's estimate. I went with a 1/8" web when I drew my plans and I think I might bump that up to a strong 5/32" when I build. My as-laid-out web at the breech is a shy 5/32" and, If I can work up the nerve, I think I might reduce it to a little under 1/8" to reduce the depth of wood under the lock. My forward lock bolt already hits the lock above the centreline, so I will need to take that into consideration. As laid out, the lock nicely parallels the bottom of the lower forestock, so I am inclined not to raise the front of the lock. I am not easily offended, so please set me straight if I am headed off on a tangent.
I was surprised to see something else in the photos Rich posted. The forearms in photos 1, 2 and 4 appear to come well above the mid line of the barrel. I wonder if that has any regional significance.