I always install the rings ahead of the hook. The hook itself is more so there to keep the motor in the rocket on parachute deployment, not so much to keep it from thrusting through the body tube. That's really the job of the engine block/ring. Not that the hook top isn't capable of holding the motor in, but like others have said, the motor tubes are generally a little flimsy and will tear over time and repeated launches if you don't have the block in place.
On rockets flying on 24mm motors, I've taken to installing the Estes screw-on retainers. After a few launches where the motor was ejected past the retaining hook, I decided I liked the more positive retention the screw-on type afford. Not that I'm particularly worried about being hit by a not-so-heavy cardboard engine tube, but they can potentially start fires if they fall in dry grass or the like. Another benefit of keeping the motor in the rocket is keeping the weight in while the drifting on the chute. The particular rocket in question that I was having issues with ejected motors was quite light, so sending it up on an E and then not having the weight of the motor made it drift way farther.