If the pouch you bought is the TT "Plate Carrier Lower Accessory Pouch" I suspect you may see a little more sway/flop-forward than average due to the pouch simply being velcro'd through those plastic slot bars. You'll have to put whatever you plan to in it and run around to be sure.

If it flops to much for your liking, send it back and get a SS SACK. It's pretty much the same size as the Haley hanger, just executed better, IMO. And if neither works for you, than likely nothing else will.

Personally, I also find top-opening pouches easier to get stuff out of than front-openers like the TT and Ferro items- stuff always gets caught up in the corners trying to get it out, harder to reach into, especially if wearing gloves. YMMV.
Something to remember, especially if worn ICW a plate carrier with mags on the front, between the plate + mag thickness, you probably will not be able to see well (if at all) into the pouch looking down on it. So if you're one of those organization freaks with your med kit (or anything else you put in there), you're pretty much going to be grabbing blind at it all.... IMHO, if I was using a dangler as an IFAK, I'd put all the supplies in some sort of easily opened plastic bag, and stuff the whole thing in there, so I could simply unzip the dangler, seize whatever my hand found and yank the whole thing out in one shot.

Obviously, do not load it up with batteries, flashlight, multi, or whatever other extras you want- I'd say 2 lbs or less would be max for comfortable wear. I mean, sure you could fill it up with whatever in an emergencey, but the heavier or the more "hard" objects you stick in there, there more noticeable the flop will be, and the more it's going to suck to lay prone on.

As far as danglers for IFAK use, I've seen a couple folks running the Mayflower/Velocity LVBOK like this, but I'm not sure if they had it custom built to be a dangler, or DIY'd it. Cool concept for thought though...
https://pbs.twimg.com/media/Cd_kwQNUIAADJNz.jpg

You could alternatively try a Manly Fanny Pouch but like ARCH mentioned, if you run it front, it can potentially slap you around a bit. Running it off to one side or rear would be better, but I can also assure you that if the minimal flop of a dangler annoys you, the more pronounced flop of the tac-fanny will irk you even more. The one big plus this does have, is you can take it off- easier to access supplies, or throw it over the top of your pack as a quick-detach go-bag. So, depending on your usage needs, you don't *have* to wear it for long periods of time. YMMV.

I'm currently using a SS SACK, and I quite like it, but I just use it as a light "extras" GP, not an IFAK.