Today people are so oblivious to what's going on around them, because they're busy with their smart phone, I doubt that any of them would even notice if you were open carrying a firearm.

I wish I could find a good mag pouch. I have yet to find one that works for me, and I don't like carrying my spar mag in my pocket, but better to have and harder to get to, than no spare mag at all.

IMO, this is partly true (obviously I'm not as credentialed as oldkim, so take that with a grain of salt). If someone say carries a G26 and wants to up to a G19 (or 19 to 17) I think that is fine. Same thing with their XD or M&P brothers. Same caliber, same manual of arms, likely the same holster setup may work.

IMO, double stack should always be the default carry, unless dress or circumstance require (or make it prefereable) to only carry single stack. Of course if someone will leave the home without a double stack, but take a single stack, then carry the single.