I'm designing and flying a 3D printed (about 90-99% printed) high power rocket for my NAR level 1 cert attempt and possibly reuse the design for my L2. I do have experience in 3D printing and model rocketry, just not combined. So the design might not be perfect...
Why 3D Printing?
I wanted to do 3D printing because it affords greater complexity in aerodynamics, and the ease of reproducibility, not only of results but of the actual air-frame. Also, its not generally done so that's all the more reason to try!
NAR is the National Rocketry Association, they are a cub for model and high power rocketry.
The certification process is in 3 stages, and basically you have to build a rocket that successfully flies with the appropriate size motor. (more details of the actual process are on their website).
This is about the top third of the rocket with the nosecone screwed into the payload bay and the parachute bay slid onto the bottom of that. These sections fit quite nicely together with minimal finishing.