A buddy of mine just gave me his old .61 airplane engine to put on a air-boat I am building. Got it home secured it to a vise that is mounted on my work bench to try a needle I have. Started it up ran it for a couple seconds, reset the needle, ran it for another couple seconds and stop it. Reset the needle crank it up ran it for a few seconds, and just as I went to shut it down, the engine come off the vise, the prop worked its way across the top of my hand. Two hours later I am returning home from the hospital with 10 stitches. It was a deep nasty cut, could see the mussels in my hand move in the cut. My advise is don't trust a vise to hold down a engine with the prop on it, to do any settings. I will be building a stand that the engine can be bolted to.
Dad did one time tell me, Just because you get away with it a time or 2, don't mean it will not later come back to get you.
I have always preached safety.