I also like the Blow out kits that are detachable from your kits, for me it is a must to have something there more than just velcro!!! you need something that will secure it in place until you need it: snaps, good retention strap with a quick release buckle.
If you start doing vehicle bail out's with any equipment that is not secure you will loose it, once you start going into fire and movement or crawling on the dirt to use micro terrain you will be surprise of the things that you start loosing and leaving behind with out knowing.

you need to make sure you put it somewhere that you can access the kit with either hand and also one handed if you need to, if you are working one handed you will need to get it away from your kit and maybe place it in your lap to have easy/fast access to your equipment and get your self patched up in a hurry.

A lot of the guys over here are using different types of detachable IFAK pouches but they all have a retention devise, there are a lot of good kits out there. I am using a SORD IFAK pouch that is detachable, and i also like the Blue force gear IFAK a lot too.

We also keep our tourniquets out of the IFAK pouches and put it somewhere in the center of our bodies to have quick access if needed, our standard is to have a tourniquet in place in 60 seconds or less our re-evaluate your gear placement and gear it self.

I know when I was still in the Marine Crops it was always: Self Aid, Buddy Aid, Medic. after that the medic would make the determination on steps to follow.