Motor mount 1st. always did it that way and nary a problem. Besides, some of my designs require me to get the motor mount done first anyway. Fins get in the way. I've used engine hooks once, in the last 30+ years. Usually I rely on an engine block and friction fit, but when I did my upscale Astron Cobra, I opted for a mount for 3 - 24mm motors. Granted, the old instructions for the Cobra was to use tissued glue to stuff between the motor tubes. Since the 3 - 24mm motor mounts were going in a BT 70, I opted for a motor mount kit that had engine hooks and plywood rings. I followed the instructions on the motor mount, (and I really wish I hadn't) which positioned the aft CR about 3/4" up inside the airframe, and I went with the engine hooks as well. (wish I hadn't done that either.) Had a great flight. Chute deployed...yadda yadda. When my brother retrieved the rocket, this is what the motor mount looked like.
Our regional rocket geek/scientist/brainiack, suggested that, the recessed CR may have created a vacuum, causing the exhaust to invert and burn up the motor tubes. The motors were missing as well. Apparently, the heat flexed the hot engine hooks and the motors shot out at ejection. The repair was finished with my USUAL aft flush CR installment. And no stinking engine hooks!