I've been told by them that know, that while some tn rifles had rounded forestocks, most were v shaped. Also, flat under the lock panels.
Be careful with that U and V forearm thing. Most guns have forearms somewhere between a U and a V. Going from a wide barrel to a narrow ramrod is going to give you some sort of a V. It is all a matter of how direct your path is from the barrel to the ramrod. The rifles of SW. VA and E. TN in the early 19th century tended to be more V than U, but I only ever handled ONE rifle that had a a real V shaped forearm and it was distinctly uncomfortable to handle. The lower forearm should be egg shaped with the broader, more rounded end, on the bottom. Thus, U shaped. The upper forearm is going to be more V shaped. I start out shaping the upper forearm V shaped and then round it off as I finish it.
You need to use an original rifle of your chosen style as your guide to such things. As a general rule, I make earlier rifles (1775-1785) more rounded than later (1800 +).
The stock should always be comfortable to handle and shoulder. To a very great extent, the parts (most specifically, the barrel, lock, butt piece, and trigger guard) and the owners dimensions (pull and drop) will dictate the shape of the stock such as how flat or not, the panels under the lock may be. The same goes for the angles of the panels at the top of the lock panels.
The lock mortice should be narrow, as in 1/8" or less. The flat portions of the lock panel in the front and back of the lock should be about the same length. You don't want a lot of flat surfaces on the lock panel. The the profile of the side plate panel should roughly match the lock panel but only really needs to be the same length, ending at the same points when viewed from the top and bottom of the stock. That said, you don't want a lot of flat surfaces to surround the side plate. Slim it down a bit more than the lock plate if you need to. I don't like to have a thicker mortice under the sideplate than under the lock.
