The supplier that does black nitride for me, they also offer a QPQ after checking with them. There are so many factors at play that have crossed my mind, and it brings me back to one of my concerns of black nitriding, which is thru nitriding of the very thin wall section on this part causing embrittlement and potentially failure. So I won’t be switching to any QPQ..
*shrug* maybe I’ve over thought the whole thing, but that is usually how I do things.