I don't want to "rain on your parade", but the West Tennesse picture is largely understood in a logical way.
The chief need for clarifying information has to do with what happened to George and Nathan Rochell Fly of the Court Records. (1828) You are (and this is not intended as a criticism) sitting on the Orphan information giving us the names of George (who may be a son of the George in March 1828)(the list of court records I have made reference to.)You are a believer in documentation.Please be willing to share the text you surely copied down when you found this record, if you possibly can. The Lavina/Lavinia/Lavinea Fly orphan we need for you to tell us how correctly to spell her name, for it has appeared in your references in all three ways.Your record MUST have given it spelled ONE way; I'm sure you will tell us if, indeed, it appears spelled two different ways in the original text. If this George in 1828 was the father of George and Lavina, it could explain why he dropped out of sight by dying. Anything but a bare index record should tell us WHO the orphans' parents were.
Please understand that there is no confusion in seeing Jeremiah and his sons William Fly, Asher Pipkin Fly and Elisha Fly go from Maury Co., TN to Carroll Co., TN before Jeremiah and Asher Pipkin Fly and William moved first to Arkansas about 1833 and on to to Missouri in 1836, while brother William stayed in Searcy through the 1840 Census and then moved to Barry Co., MO to die in 1849. (Mortality Tables.) Census records for one and another of their children tell us where the different ones were born (as to state) so that you can pin down when the three made their moves along this trail.
I can get absolutely NO intimation of the introduction of any of the Pennsylvania Flys of the 1840 period going to Tennessee, nor any indication of any infiltration of Cherokees who are connected to Flys out of Georgia at this period. There WAS such a designation of CHICKAMAUGA Cherokees, but I have seen nothing to create a connection of any Chickamauga Cherokees to our Flys. (I believe that references to "Chickamonga" Cherokees is a corruption of "Chickamauga".)
I am not saying that you may or may not be onto a promising line of research, but it appears to me that we have a nest of "sunny-side-up" eggs here and your approach is trying to "scramble" them.Why do you not immediately see Jeremiah, William, Asher Pipkin and Elisha for who they assuredly are, our Pioneer to Tennessee (Jeremiah) in 1796 and his THREE sons. Unnecessary complications are distinctly unneeded here, when it looks quite straight forward.
Hope you have a Happy New Year.It has been recommended that it might be a good idea to refrain from using the computer on Jan. 1 as a possible way to avoid any virus someone may have slipped us intended to "go off" on 1/1/2000. What do you think?