So I think I've narrowed down this whole MARCH belt and thought I'd share my layout and brief description of contents. This piggy backs off my aid bag and gives me quicker access to supplies. If you haven't considered a MARCH belt, I hope this is somewhat helpful. Aid bag still carries my advanced stuff and diagnostic tools but now has a bit of room for sustainment items. I know some other guys carry blood and warmers on their belt but that didn't work for me and frankly was too fucking heavy and bulky. This is definitely mission specific and I have about 5 other aid bags and waist packs depending on what I'm doing.
This is a Gear Dynamics Modular Gun Belt system with assorted pouches.
L->R: multitool, M4 mag, "M" pouch, "A-R" pouch, IFAK, "C" pouch, frag, TQ
"M" pouch: 2x pressure dressings ("commando" style - 6in OALES stripped and stuffed with Combat Gauze), 2x z-fold kerlix
"A-R" pouch: 1x NPA, 1x cric kit, 1x suction, 2x 10ga NCD, 2x 14ga NCD, 4x chest seals
"C" pouch: 2x IV starter kits, 2x NS flush, 1x 20cc TXA flush, 1x EZ-IO
That's it. Again, I hope it was helpful for those considering it and didn't know where to start.