Maybe use a nipple/cap cover/protector. But you have to remember to flick it off before you fire it though. But practice to make it automatic with the reflexes is a good way to do it. It is not unlike you practicing flicking the safety off on a modern gun to fire it.
the muzzleloader version of a .41 caliber derringer was close to being the same as a .41 Rimfire short cartridge version. There are some references and tests done years ago that showed the .41 rimfire short cartridge was more powerful than people thought. Ballistics isn’t something to write home about though. It used a little over 8 grains of BP with a 130 grain bullet. Depending on the source, muzzle velocity was between 425fps to over 685fps. I suspect there was quite a bit difference due to the age of the ammo and or the type of BP used. But even the low speed rounds went all the way through a wet five inch thick phone book and a piece of thin plywood too.
https://en.m.wikipedia.org/wiki/.41_Short