Carrying with an empty chamber sounds great...until you get into a situation where you cannot work the slide.
One example (on The High Road, I think), a guy was charged by a dog. He drew his gun and had trouble working the slide under pressure. Fortunately, the dog didn't attack him.
What will you do if the goblin is on you and is punching or stabbing you? Worse...what if you're cornered? Cornered can mean that you're in a parking lot, standing next to your car with the door open...there are few places to run. Criminals wait for such opportunities.
Load your gun and get training. There is ample opportunity to get the skills you need to carry the gun properly.
SERPAs are crap. I took one to a training course (http://www.fpftraining.com)
and a rock got into the lock mechanism. I had to take the holster off and work the rock out with a knife...which took 10 minutes.
Furthermore, your trigger finger should be indexing on the gun, not fooling around with the retention gizmo.