Shumway openly stated that thought process in RCA - i.e. there are examples where he stated that certain guns were assumed to be southern solely by virtue of them not lhaving features that made them easily associated with any of the well known gunmaking centers of Pennsylvania. And it worked both ways - there are rifles attributed in RCA as southern that are now believed to have been made in Pennsylvania, and some rifles attributed in RCA to Pennsylvania or unknown that are now believed to be southern.
In the early period especially, there was a lot of migration southward from Pennsylvania along the Great Wagon Road. Wallace's research has also put forth some interesting new ideas on the possibilities of two-way sharing of riflemaking concepts along that route as well, by way of Virginia riflemen carrying guns, ideas and in some cases gunsmiths themselves north; intermarriage of Virginia and Pennsylvania gunsmithing families, etc. Simon Lauck is one really interesting example in this regard.
There was a large migration from Virginia and North Carolina in the late 1700s and early 1800s for points west - to East Tennesse, the Cumberland plateau and central Kentucky, so the spread of these ideas after the revolution continued. Consider Joseph Bogle - from York County Pennsylvania, moved southward through Rockbridge County Virginia and ended up in Tennessee. Or John Bull - born in and probably trained in Maryland, and ended up in East Tennessee and ultimately northern Alabama. Think of the influences they were exposed to growing up, traveling south and west, and finally working in areas that were the gateway to the southwestern frontier, with folks from many points east and (with their rifles) moving by and into their regions all the time, yet still isolated from many of resources, and competition, that were in the more populated areas to the east.
I was once told by someone at the TVM booth at Friendship that the "Early Virginia" hardware was actually based on a Hershel House iron mounted contemporary piece. (This is a popular style of Hershel's - check the guard and buttplate on the CLA raffle gun from 2 years back). Hershel has a knack for absorbing original influences and creating something unique of his own. When I look at the guard and buttplate I see the possible influence of several pieces, including the Haymaker guard with it's long bow and that oblique angle on the inner front of the bow. Also, to me, that buttplate with the rounded heel looks lto me ike it was influenced by those parts that came out of the grave in Alabama and are believed to be southern and included a captured lid box, which you start to see on some Virginia-made pieces by the 1780s. Wallace actually attributes the grave relics in this case to be of Salem NC/Moravian origin in one of his Muzzle Blasts articles.
Guy