Dewey Vicknair on American doublegun designs...
https://vicknairgunsmithing.blogspot.com/2016/01/an-unbiased-look-at-design-of-american.htmlBrutal, but hard to argue with.
I'd read this a few years before but looking again, this time with a renewed interest in an older American (possibly Damascus?) SXS target gun. 1894 Remingtons and Fox pin guns certainly look promising, perhaps even the bigger Parker no. 2 frame guns? My brother has a long, heavy, 1930s Field Grade Elsie that I can secure quite reasonably that would likely work, but after reading Dewey's screed on them...