I shoot percussion doubles without any problem. That is a lot different than shooting a flintlock. Lefties need LH flintlocks, for both comfort, personal safety, and shooting skills. There is a learning curve for all shooters when they begin to shoot flintlocks, and it often takes a year of shooting before they stop looking at, worrying about, and being distracted by the flask in the pan.
The only good thing about that time is that this is also about the same length of time it taks a new flintlock shooter to become proficient at loading and priming a flintlock consistently, so that he knows the gun is going to fire every time, and just shoots the gun, concentrating on all the other things that are needed to put a bullet where he aims.
I went through that process more than 25 years ago; my twin brother just went through it in 2004. He was concerned, dismayed, and frustrated at the problems he was having flinching because of the flash, and other problems he was having making his gun go off every time. He consulted me by cell phone from the range, almost every time he went out. He relied on my advice to get him over the hump. After one year, he found he was shooting his flintlock well, the flash no longer was a distraction, and he was not having to use a checklist when loading and priming his gun to get it to go off every time. He is now an enthusiastic " Rocklocker ".