Should not be an issue with a modern gun
First off, most defensive use of CCWs is typically 1-2 shots, sometimes 3. (actually, they are rarely fired and the revealing of the weapon almost always makes the badguy turn tail and run or realize you still get to be alive in prison, so they give up.)
Second, one in the pipe is fine, considering the stress you'll be under if you're in a situation that warrants it, racking a slide may seem like an eternity to get done. However, I have a DAO and DA/SA, so I would choose DA with one in the pipe for carry purposes.
Third - I've placed a single round in the chamber of my PT145 and 10mm Witness and snapped the slide shut by releasing the slide lock. No issues encountered yet, or looseness noted in parts because of it. But these are both external extractor models, may not apply to an internal extractor models.
I usually leave my mag 1 or 2 short just so I don't compress the spring as much, in hopes of giving it a longer life on nightstand duty. (or so I've read, may be BS) However, when I carry it in the car and stuff it under the pillow while on camping outings, it's running on Full with one in the pipe.
jeepmor