Agreed. I've almost died, and I've seen more than a couple lifters come about 1/2" from being decapitated when a bench goes wrong and the spotters are slow on the catch in competitions. I am glad the back spotter I had in training saw what was going down and was ready, because everything felt fine to me until the last second. I was amazed at how fast it went south (turns out I wasn't on the "bubble" properly, but it FELT like I was).
That bad a dump has only happened once to me, but once is enough to drive the lesson home.
That being said I suppose the power rack could be useful for benching. I was thinking regular bench. It will be awkward getting the weight out and staying tight, but if it's all you got do it. I would just set the power rack pins to a 1 board or something--that way if you dump you know it can't hit your chest (difference between a 1 board and chest is negligible when learning a shirt, so it won't hurt your training). Hell as far as learning a shirt goes I'd stay mostly to 2 board presses to start the technique training because it is so different from hitting the bottom in raw benching. Much more work to keep stable.