I would be leery of having all of my mags open topped, especially with the feedlips up. If you take a spill, vehicle rolls, etc you can lose mags or get them fouled. I always run a first reload open topped but the remainder with flaps.
While running mags with the bullets up makes for faster reloads on the rock-in style mags like VZs or AKs, the top round will work it's way off the mag over the course of the day. I tried this on some open topped Paraclete pouches until I got tired of moving the top round back into it's place and eventually just flipped my mags upside down.
For range use though it can save time on reloads having bullets up, depending on the style of pouch.
I can hang my vest upside down and shake it and the mags stay retained with only the horizontal retainment. It seems to be working, for me anyways.
It's a familiar rig for me and muscle memory is important.
As for the splash/crash retainment, luckily it's not something I have to worry about anymore, and it's nice to be able to think like a civvi and take the top bungees off now.
... I wouldn't jump with this rig, but It fits the bill for my current station in life.



















































