I have a T/C PA Hunter, .50 cal.
So, Bobby Hoyt increased the original barrel to .54 cal and that works great.
Also, he made a .62 cal/20 ga smoothbore barrel for it.
Not being a flint lock fan, I replaced the L & R replacement flintlock with a L & R Replacement Percussion lock and added a drum and nipple to the barrels and it shoots great now.
I see no problems with the 20 ga barrel.
John