I'am a lefty, which doesn't usually make much difference to me, when shooting most modern rifles, even boltactions, and semi-auto's, other then the occasional unfriendly safety which I have been known to get changed, when I can. And all of my caplocks have been righthanded, but the Flintlock: I don't know.
Do any leftys on here shoot righthanded flinters, and does the flash, etc matter to you, that much? I never had much problem when cocking the hammer on a caplock, but I would sorta expect a flinter to be a little more unfriendly to pull back when on the wrong side.