Looks Good!
I have a method to doing my fans and it works out good. I use the foam Home Board for insulation. I have a few lines drawn to keep every thing "centered" and depending how many feathers are in your fan will give you a center line (odd number) or a split (even number) plus the bottom line is a square to the others. I'll mount 10-20 fans a year, and get quite a few compliments on them.
MK M GOBL