Lot of good steering already going on but I'll add some details.
I have a plate carrier for work. I carry a magazine loadout on it and, for a bunch of years, trained loading from the leftmost pouch and then backfilled across as required. I bought a chest rig (an old SKD/Eagle combo that I really like) to train with when i didn't want to be lugging the armor around.
Fast forward a 10 years and I realized how much more efficient I am with a belt mounted pouch (yeah, I'm a little slow). Likely a benefit of all the cross pistol training, but regardless... that's now my primary reload and I backfill it from the chest if I'm kitted up.
And, btw, I still use the chest rig as a dedicated SAR setup and would highly recommend it if you're stuck on the original idea. They don't make an identical one anymore I don't think, but there's one that's VERY similar in their PIG line.
ETA... Had to look it up; it's called the PIG UCR (universal chest rig).