With some more recent weight loss, I have now been able to carry a Back Up Gun on a more regular basis. I've started trying out different guns and styles, and have come to 3 conclusions.
1) Crossdraw works for me. Accessible by either hand, easy to get to seated, and quick to access. Now I need to find more decent IWB crossdraw holsters. Suggestions would be appreciated.
2) I carry spare ammo for anything I'm carrying. The whole point of being prepared is BEING PREPARED. Spare ammo is part of malfunction clearance, and if I have already gotten to the point of needing a gun, then needing ANOTHER gun, things have probably gone so far sideways that I will probably need spare ammo for that second gun for a reload or malfunction clearance.
3) If your main and BUG do not share ammo and magazines, then your BUG needs to have a totally different style of reload. If you are carrying a Glock 22, and have a Glock 27 as a BUG, then you are cool. But if your main is a CZ-75, and your BUG is an XD compact.... it would be easy to confuse the magazines under stress. So, if your Main uses a double stack mag for reload then you should carry a BUG that uses speedloaders, speed strips, or even just a single stack magazine. Either carry the same reloads, or totally different.
Just my thoughts.