I have read that the popularity of the back action was do to that it was cheaper to produce .
I also have read of the back action called a French lock . Now as I understand it , this dates back to the flintlock AND full stock rifle .
Two American makers that come to mind would be Samuel Smith there is one of his rifles in the Laidacker collection that actually has 2 back action flint locks that fire two loads from one barrel . The lines are very much along those of Issac Hains though the comb line is much straighter that rifle is I believe dated to 1805
Or there abouts
Another maker that comes to mind would be a man named J Hoffman who also produced full stock rifles with back action locks .
Now as to the question .
No Russ I don’t think it would be out of place at all as long as you not looking at copying leman .
There are a lot of examples of target rifles that have a strong base as plains rifles . Its easy to see the evolution there .
Past that one of the most wonderful rifles I ever saw was a back action made by a maker named Andrew Waffling . From Pennsylvania.
I saw that rifle up in Cody the last time I was there , simply wonderful half stock . Silver nose cap and belly inlay , toe and large brass patch box
There is a black and white of it in Dillon”s “the Kentucky rifle “
You will also find black an whites of some others as well as the two makers I spoke of above that have full stocks .
half stock do though show a more common use
I would also recommend if you can get or look at a copy of The Muzzleloading Cap lock Rifle , By Ned Roberts . Its full of back action half stock rifles both target and simple plains rifles
So IMO what you would be doing would not look out of place , was done , very often .
Maybe not by Leeman but enough other makers who had rifles similar that yours would pass.
i would also say this . the back action needs a heavier wrist area so you wont be able to take it down as much . well you could but they would be prown to breakage . but again it can be done and was done
as to old sally joe meaks rifle . if your refuring to the one in the Oregon musuam claimed to be old sally , there is alot of discussion and actual some pretty solid proof that it is not nore can it be old sally . while it may have been owned by joe meeks , it apears do to its markings and numbers to actualy be a german contract rifle from the texas emigrants
OHHH and russ , i bet i have a couple dozen original back actions .
you pay the shipping cost or wait tell Monroe and any one of them is yours .
you want a dubble screw or single screw