Thinking about a Drop-in Flintlock Barrel

I Have a T/C Hawken .45 That I got new in 1979. I've been thinking about getting a .54 round ball barrel for it, It's a 15/16"barrel channel. I've seen the green mountain barrels and heard good things about their drop-ins but the only barrels that I have been able to find in .54 are percussion. I talked to Rice a few months ago about building one, they thought that a 15/16" barrel weight was ify for a .54. Today I spoke to Suzi at The Gun Works, they sell Oregon barrels; she said that it wasn't a problem, all that I had to do is to let her know the Barrel length, Caliber, rifling twist rate, and the locations of the dovetails for the sights then send her the stock with the lock so they can properly breach, install the the touch hole,under luge, under rail and ramrod pipes. $350 in the white. The barrels are in a 6 month wait time.
I do have a few questions for builders, shooters and hunters on this forum before I commit. What would y'alls recommendations be for barrel length, Twist rate and rifling depth? The the rifling depth offering is .010"-.014". My original barrel is 28" I was thinking about a 25' or 26" barrel (should lighten it up a little) with a 1:66 or 1:70 twist but I'm not sure what optimum rifling & depth should be for a short barrel .54.
Oh, and has anyone here have done business with The Gun Works Muzzleloading emporium? Thank you for your input in advance.

I would lean towards a 1-56 or maybe 1-60 for a round ball in a 54. The slower the twist the more powder usually required for optimum accuracy. I have a number of 1-48 TC 54 caliber factory barrels and even with their shallow rifling shoot roundballs fine. Two of my favorite TC barrels are rebored 58 caliber 26” barrels in both flint and percussion with radius bottom 1-60 rifling. Both very accurate with 80 grains of fff Swiss. Had a 1-72 58 caliber years ago that needed 120 grains before it started to get happy. Fun was pretty much gone at 100 grains.

As far as barrel length, prefer the shorter barrels (24”-26”) for hunting and a bit longer (32”-34”) for target.

Thank you.

Keep in mind that a 28" .54 barrel will be around .60 pounds lighter than a .45 barrel.

I have done business with them and they were accommodating and good communicators. My own experience in getting what I want out of a .54 was to go with a 32-34-inch barrel and 1:70 ROT. I shoot PRB, I want accuracy and a medium load with good velocity to shoot out to 100-yards plus. I started with a GM 40-inch barrel but over time have cut a few inches and re-crowned, then some more. A few inches at a time, I have settled on 33-inches. I only lost 45 fps from the 40-inches with the same 80 grain load. The accuracy is superb. My 28-in barrel .54 uses the same load but it is a totally different barrel (not one that I used and cut, used and cut). The MV is 45 fps less than the 33-inch barrel. Length may play some part in that but there are other factors too being a different barrel altogether. You might think hard on the length and twist. It is a tough decision.