Rocket Engine Mount

I am helping my friend build a 3 stage model rocket for his Earth and Space Science class, so I thought I should share the wealth. This thing is still a work in progress, and we have not actually built or printed any of the parts yet. I will update this post as more of the rocket design is completed. I would love to hear what you guys think about this project in the comments.

UPDATE November 11, 2016: I am working on getting the Customizer app to function properly.

UPDATE November 12, 2016: I have fixed the the code to work with the Customizer app. I removed the "Global" tab and converted all of the fractions to decimals, so it seems to be working now.

Parts list:

Rocket Engine Spacer:
-This spacer is used to hold the rocket engines for the first stage of the rocket. It can be customized to fit all sized of rocket engines measured in both inches and millimeters.