Using the wrench to get the props good and tight is the best way to prevent one being thrown off during braking. If they get too loose from repeated removal after overtightening, just replace them. The new all plastic composite interior props are 1/4 the cost of the old ones that had metal threads inside! Consider periodically replacing them as a regular maintenance item, even if the blades still look like new. The interor cushioning of high end running shoes wear out long before the exterior tread ever shows signs of wear. Same idea.
Please do not use the wrench to tighten the props. It's included to only remove the props if they are difficult to remove.
Spin the prop on and then snug them up by hand. This is all that is required.