I was really looking for what was in the training. From there was there any general practices that developed.
Yes the carbines were delivered with 2 magazines plus the one with the gun. When the carbine mission was expanded beyond a defensive weapon, clearly those troops carried far more magazines.

There's no question that in high stress situations theory and even training doesn't always work out as planned. The decision not to incorporate the hold open in the follower is a given. I haven't seen the reason for that documented. The fact that its not easily observable and the reportedly increased stress and wear are two reasonable factors that may have weighed on that decision. It's hard to imagine there was not some thought given to tactics.