Do the hpg bags cause any sore spots or chaffing with heavy sweating?
This can be a problem and just about any chest rig (like this, not necessarily a holster) will trap heat. I was actually more concerned with perspiration affecting my handgun than discomfort, but this can be a problem for some. With that said, all our longer backpacking trips of multiple days are during the heat and humidity of Southeastern summers...it's just something you learn to tolerate (I'm not originally from GA) and deal with. As soon as it heats up, my whole upper body is soaked even with a vented frame backpack, so I've learned to tolerate the Kit Bag.
The good news is that I wear my Kit Bag under my backpack's frame and suspension and never had any issues with chaffing. I would caution you to avoid over-weighing the Kit Bag, it balances nicely with a pack, but I try to keep weight to 3-4 four pounds maximum.
The other issue with the HPG setup is that at the moment of obtaining your purchase on the grip of your gun, it's pointed at your off-side bicep. Their video used to show an awkward offside-elbow-high draw but I don't see it anymore. If you're confident that you will remember all that during a high-stress draw; it may work for you.
There's no denying there is some inherent risk when drawing from the HPG Kit Bag. I've tried a couple methods, the easiest is to just swing your arm down to your waist and out of the line of the muzzle; however some drills don't always make this easy. The other "drawback" is that this is much like carrying concealed in that you need both hands to quickly deploy your handgun; much like pulling or sweeping your shirt back, you need your weak hand to rip the holster compartment open for quick access. Another reason I like the Vanguard trigger guards is that you obtain the same grip as an open holster (trigger finger straight and high on the frame) and pull the pistol from the trigger guard before getting your handgun lined up for an encounter. There's some debate on the design of the Kit Bag that concerns some...it's understandable, but there's a certain amount of risk carrying any firearm and there are some limitations when you choose to carry concealed. You can train to mitigate much of the risk just like any other system, but at the end of the day, you're the one that needs to make that decision.
As Mainsail pointed out, it's not for everyone and doesn't work for everyone. An open holster on the hip belt would be the fastest, but I do agree with Mainsail that a covered holster like the M12 (or, the Kit Bag in my case) is really a good idea when hiking overgrown trails or rugged terrain. The covering keeps a lot of debris and mud out, not if but when, you take a spill with your pistol taking the brunt of the fall. For concealed carry, this has just worked best for me and the locations we do a lot of backpacking.
ROCK6
this is a "Roy's Original" pancake. It offers good protection for the gun. Options of cross draw or Strongside. It is one of my favorite holsters.
You can buy repro military style M3 holsters for not a lot. They can be worn a couple of ways, one of which places the gun at the lower left of the abdomen, above the belt line (high cross-draw). I find it keeps it out of my way while scrambling, and the pack straps don't get in the way if I have one on. They will fit more than just the 1911, you may have to work the leather a bit. The one above is an original, not a repro.
Highly recommend http://www.simplyrugged.com/
