As a lefty, I've come a jagged course with flintlocks. I bought my first, a .50 cal. TC Hawken about 25 years ago. I couldn't shoot that thing for squat! I flinched everytime that lock decided to work,and the flash went off in my face. I sold that rifle and bought a Hatfield .45 cal. from Cabela's. Again, I didn't know that left-handed locks existed. That rifle was perhaps the worst firing piece I've ever owned. It was pretty, it was light, but getting it to fire consistently was nearly impossible. I shined and polished the Hatfield, and sold it to a fellow I didn't know, thankfully. With the proceeds from that sale, I bought my first lefty rifle from Brad Emig of Cabin Creek Muzzleloader, and found I could actually shoot a group and take a deer.
Now, after shooting and hunting with lefty rifles made to order, I find a .54 cal. Yorktown, built by Brad Emig, with a 39 in. Green Mt. barrel, 1 in 60 twist, just about perfect. I shoot a .535 ball wrapped in a .015 patch in front of 80 grains of FFFg Goex. It works for me.