Hello,
I broke a rib last year (end of season fortunately!) while having an impact vest (I can not remember the brand, and the vest is too cold and wet in the back of the car to check now

) and a wet suit. Thus impact vest may not protect you from everything.
I missed a high jump, the kite did a serious loop in the power zone and I 'landed' ('crashed'

) fast, hard and badly on the ribs.
However, i kind of remember that the pain started at the take off, and then strongly increased at the 'landing' phase.
I used to significantly tight my harness, and I wonder if the spreader bar pushing my ribs up is not the cause of the injury during the take off, more than the 'landing'. Thus, I wonder if tighting the harness very much precludes sufficient movement of the impact vest over the body and ease breaking ribs? I am not a doctor and I have no idea about the relevance of this thought. I can not suitably remember either.
Anyway, I am now carefull not to tight too much the harness. Heaps of big jumps since, lots of crashes, but remaining ribs still in one bit! Yeah!
As said Bowsky, the former broken rib still hurts from time to time (and also sticks out a bit under the skin). But that's ok

.
Be careful!
Fred