I certainly agree, the profile of the modern guns does not match the originals.
However, speaking from experiences both my 1870’s vintage percussion double and my 1880’s cartridge gun have the classic 19th century stock drops, and unless you are willing to learn to shoot in the “gentlemanly manner”, that is, head erect, shoulders back, you will most likely add a lace on comb.
Yes, I know people who can handle these old timers with little difficulty but I am not one of them. I shoot a lot of modern skeet with a straight hand, double trigger side x side but switching to the old style drop just does not work for me.
Perhaps if I only had one gun I could adjust but I do not expect the firearms makers to return to the older stock dimensions any time soon.
I will have to defer as to how common the percussion double was out west in the 1830 to 1840 time frame. They certainly were available.
My reenacting interest centers on the southern Great Lakes a century earlier.