Rolf,
The Bedford style locks with their long tails and graceful hammers are only found on Bedford Co. rifles with maybe a few exceptions of Somerset Co. rifles just across the western border of the county. Barrels on those rifles were typically straight as the rifles date a bit later than most of the ones we typically discuss but you could use a swamped barrel, have a more useful rifle and no one would object. The rifles are slim so I wouldn't use anything heavier than a B weight barrel. Rice's Beck pattern barrel would also work. It's 1" at the breech and has a more gradual swamp. I know you like silver work so in percussion rifles some Huntingdon Co. rifles come to mind - perhaps because I grew up in Huntingdon Co. However those rifles have very small curved butts that require shooting from the arm and not the shoulder so they're probably not what you're looking for. Calibers on those tend to be small, 36 -38, barrels straight, often at 7/8" and in the range of 38-40" long so they are quite muzzle heavy.
If I wanted to build an ornate rifle with lots of silver work I would consider a southern rifle. Jerry Noble pictures some, northern Georgia as I recall but may be wrong, that are ornate by any definition and have sleek, elegant lines. When I get a chance I'll dig out my books and pick a few out. If you want I'll scan the appropriate pages and send them along as a file.
One more option would be a western Pennsylvania rifle - Westmoreland or Allegheny County. Some of those rifles have some of the flashiest patch boxes ever used as well as a moderate amount of silver. Butts on those are curved but large and I don't think there would be any problem shooting them.
For any percussion rifle in the late flint early percussion period, say 1830, lots of inlays, carving at a minimum, I would build a fairly small caliber, certainly not bigger than 45, as these were primarily squirrel and small game rifles. The weight will go up with the smaller bore but that's in keeping with the original rifles.
Tom