Hi Tom,
I was just thinking about the grip safety, too.
The problem is that the HK USP does not have one.
But, I know what you mean. As long as the controls and trigger are safe with the holster, everything should be fine.
It's getting into the right frame of mind that is slowing some of us down. I really prefer the single-action mode. There's less chance for the pistol to wiggle around while you are pulling the trigger.
I even keep trying to pull the hammer back on my S&W 642 J-frame, but it's not there.
Bill