Octagon,
I have a .54 fullstock flint 1" across the flats at least 42" long, I will weigh it tomorrow (Tues) it is not too heavy for me but then my off hand rifle weighs 13 pounds, I'm used to shooting heavy rifles, I like the way the .54 hangs, if you are used to a heavy rifle you will like it. Most guys that only hunt pick up my rifles and can't believe I shoot them off hand, I've found the more you shoot the heavier the rifle you want, my first serious target rifle weighs 9.5 pounds and feels like squirrel rifle to me now, I've probably put 40,000 rounds through it since 1980.
Regards, Steve Chapman