I am building an Isaac Haines kit from the Chambers family (I say "family" because when I call or email, I usually get Barbie or her mom -- both very friendly).
The Isaac Haines rifle is 54" long while their early Lancaster rifle is 6" longer at 60". When I spoke to the Chambers' about what I intended to use it for (hunting in Wisconsin), they recommended that model in .54 caliber. At first I was worried about the .54 caliber being too big but then I realized that would make the barrel lighter (more is bored out
).
I've been working on my build since November and am now just working on my carving skills before I cut into the stock so I have a good idea of the overall feel of the rifle. To me it feels pretty quick handling and fits me well and I'm 5'8" and weigh about 170.
As a comparison, I held my brother's Thompson Center flintlock the other week and that thing weighed a ton. I think the swamped barrel in the Chambers kit really makes a difference with the weight and balance.
That's just my 2 cents but figured it may be helpful.