Shoulder bag

[Jellybean]

I think folks are missing the point that a claymore bag, six mag bandelier, etc are all wider and do not have the flexibility that the IOTA has. I'm guessing they didn't look at the picture.
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There is no fumbling for mags, as it has two external mag pouches that are very easy to access with removable velcro flaps if you don't want to fool with them.

And it's got just enough room inside for some pistol mags, a flashlight maybe a tourniquet. Or you can stuff it with additional mags as it's exactly the right width to hold 30 rounders vertically side by side. (But that's not something I do for home defense setup)...........

Maybe just fog of internet, but yes, that is exactly the point[s] I was agreeing with in regard to the IOTA bag.
Like I said, that's all why it's one of the few "rapid response" side bags I'd ever consider.

My main gripe is that it's easy to leave the outside pocket unzipped and have stuff fall out. I've learned to check it, but I think a different zipper approach would have worked better. That said, the side zipper is very handy as that pocket has loop and I sometimes carry a BUG there.

I am really bad about buying oversized packs, especially ones without frames. So I've learned that bigger is usually not better when you're not backpacking.

The ADAPT pack can carry a rolled up rain jacket, a light fleece, a water bottle, some snack bars, a small first aid kit, a USB battery charger and small cable, etc. And still not be too bulky or heavy.

So I keep one in my vehicle. But I also use another one extensively when I travel. One of mine in a non-tactical color has been in a dozen countries.

Yeah, that's similar to what I did with my ADAPT - I liked the slightly larger internal capacity Vs a Yote style beavertail bag, because it allowed me to go from "light assault pack" to "go to town" bag without having to strap all sorts of other pouches to it to get a larger capacity.

I actually liked the side-zip configuration on the secondary compartment - as you mentioned it's velcro backed, so you could slap a holster in there for town use, or stick 3-4 rifle mags in a BFG velcro-backed mag pouch for assault pack use- they fit perfectly to slide out the side of the bag, and left the rest of the pocket open for other stuff. But then, I never filled that pocket with small things so, stuff falling out was not an issue for me.
What I personally hated about the ADAPT was the inner bottle pockets, and the meh molle configuration on the sides.

Yeah, I think a lot of people that buy really large packs for "go to town/EDC/Bail out bags" would rapidly come to their senses once they actually put the thing in their vehicle. IMO, there is very much a "to small to be useful" threshold as well, but once you spend a little time either trying to heave a massive bag out of the car during a training drill (especially as you mentioned, non-framed. Ouch...), OR trying to maneuver it around inside the car to get stuff out of it while in the vehicle... it becomes rapidly apparent you got to get brutal with your packing list if you want the concept to actually work.
This is what cratered my "brilliant" plans for an SBR bag - once I added even a simple selection of "go to town" stuff (not even getting to a "walk home bag"), it was just getting massive.

The down side to battle belts here is they are typically sized to go over pants and often these days have an inner belt so unless you also have suspenders they can hit the dirt when more or less "robed" where as a shoulder bag you just loop over your head and its not going anywhere.

Well, not exactly- the BB's I was talking about ARE the 'old school" molle sleeve/inner belt type. Not sure about all brands, but HSGI's Sure Grip comes in multiple sizes.
Other outer molle sleeves I've seen for use with an innet belt also aren't long enough to fully wrap around me by themselves (and I am pretty skinny), so it's still up to adjusting the inner belt to get the sizing right.
So, there are options for a BB to use when trying to be mean fast and nekkid.
Since the end user for this sort of use is not going for a full light-infantry style load, a little less molle space shouldn't be an issue, and won't require suspenders for weight.