The newer Byron fans--not sure just when the change was made--beefed up the center section of the hub. The newer 91's were capable of spinning the centers out of the older designs. Spun 3 of them out myself. Look to see that the center portion of the fan has a raised surface, approx 1/4" in height.

I have never thrown a blade, except when the center section failed and I have been with the Byron stuff for a long time. 20 + years now....

A Byron fan could be damaged when installing the fan on the engine. Holding the fan on a table top and trying to tighten the nut on the shaft, you could put enought pressure on two of the blades to maybe fracture one if you were not careful.....but otherwise..........I have never had a problem.