I'm a new builder but I've studied longrifles especially southern guns for several years.
First off it's a nice piece that I would be proud to own. $1200 is a steal for this rifle.
Here is what I see that could be improved.
The rifles biggest fault is the buttstock. It actually looks to have too much drop and too low a comb. Note the bottom line of the stock from the wrist to the toe. Note how this curve does not match the flat comb. As the flat comb goes to the heel, the bottom of the stock drops away too severely making the butt area very wide.
Look at a John Phillip Beck rifle. I can see similarities in your design. The top comb line of a Beck is roughly parallel to the bore. The top line of your comb is parallel to the ram rod. If you placed the top line of your comb where Beck did, the rifle would look like a boat paddle. I mean the distance between toe and heel would be too extreme. This also makes the comb appear to close to the lock and too low on the wrist.
You must have a good eye, because somehow it works with this rifle. If that butt was 1/8 inch taller it would not have worked.
You could have revealed more of the barrel flat.
You could have revealed more of the ramrod.
The lower forestock has plenty of wood on the bottom that could have been removed.
The lock panels looks a little large. They could have been brought down some as the front of the lock appears deep in the inlet.
Looking from above the wrist is thicker than the width of the rifle in front of the lock panels. This should be the same or very close.
I think the attempt is a very early southern rifle.
The overall stock shape suggests to me Rev War era.
The lock may go as early as 1785 but it's a common style on 1800-20 rifles.
The guard looks post 1820s.
I like the finish and I love the wood. The metal finish is excellent. Again, I would be proud to own it.