Now the exciting moment came as the motor can be mounted.

FIrst, I measure the depth of the motor from the prop washer to the rear. That become the location of the firewall on fuse. I then draw one line at either side of the fuse. I allocated points on those two lines about half inch between consequent two points. Setting the fuse on the table and put a ruler against the fuse side, I measured the distance between the straight edge of the rule and each point allocated. The measures allowed me to draw a firewall template on paper. I was able to get a very precise template in one step.

I decided to use Himax F3A 6330 motor as it was just introduced to the market and has the same mounting pattern as other more popular outer runner. I figured I can always go with a better motor later on.

Shown below are the installed motor mount / firewall made from 3mm aircraft plywood, and Himax 6300 installed on the new mount.