I have 3D-printed a motor mount and have also used four birch dowels between the firewall and the X-mount on the back of the motor. However, sometimes you'll need the extra weight of those popsicle sticks because of the light weight of electric motors. Sounds like you need to check the balance of that prop and the spinner.
Tim, great informative videos. I do have a gift I would like to send you . If I could get an address. I think you might enjoy an item from back in the day.
Yikes! That's a lot of wood, glue and weight. No criticism of Tim, but the engineer in me would like to see a lighter alternative using popsicle sticks which are a nice strong option. The nice thing about modeling is that we can each choose what we want to do. Keep up the good work.