For a successful launch, you'll want to add a little weight in the nose. Note that if you use an engine with a delay charge, your rocket will likely disintegrate in mid air :)

To secure the motor, I put a single turn of electrical tape around its base which creates a nice snug fit.

Test launch video: https://youtube.com/shorts/xUej_iEHGNw

Print the rocket body in spiral mode.
Layer height: 0.3mm Layer width: 0.5mm Top layers: 0 Bottom layers: 0 Infill: 0

Print the cap however you like, but not in spiral mode.