I first got into into 'big' control line plane with an old profile given by a friend. It originally had a .35 engine but I was going to use an electric motor. I didn't want to 'destroy' the front of the plane in case it was not for me and ruin the plane. So I made an L shape wood mount that fit the motor bolt pattern and the engine bolt pattern on the plane. It worked well enough but it needed to be repaired a few times :-) I then got the idea that I could design and print one instead. So here is what it looks like. I design many versions (using Fusion 360) for different motor bolt patterns and different thrust angles.
I had many flights and it worked well for me and it was easy to replace after a not too smooth return to earth... It served as a fuse and protected the plane.
It was also easy to try various motors.
You could try the file below or take ideas and design your own.

Xavier

Cool. Thanks.

That's awesome thanks for sharing.

Is that PLA or PETG?