I've carried my CZ-75b like that a few times. My IWB holster wasn't here yet. But it was while I was waiting on the new mag release for my Kel Tec PF9 so it was either carry the broken gun that wouldn't hold a mag or the cz without a holster.
I was actually surprised at how well it stayed in place. I had it sitting at about 3-4 oclock on my waist and pulled my galco gunbelt tight over it. Carried it loaded with the hammer cocked and safety on. Carried it for about a week and it never shifted any more than it does in my iwb holsters.
and I have a hard time imagining an event that could flip off the safety while its in place.
Still don't think I'd carry something without a manual safety that way.
I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.