Nice box set up there, I have seen those before as well, Some guys at our club uses the same type set up, I've always been impressed with it, it is definitely a Safer way to start these things, but like was said above, anything is dangerous, just have the respect. I like standing off the side behind the prop, I'm never in front of it, EVER,,, those props fly right off the engines at the most inconvienent times, usually your face takes the shot as it tends to climb when it leaves.
I only speak from experience. a 1 Time experience for me personally, countless for others.