Update Time:
I ended up not being able to open the window as it was painted shut (over 3 layers of paint). I ended up knocking one of the square panes of glass out and then mounting the board directly over the window with a hole cut right where the pane of glass was.
This ended up being a better situation because if my calculations are right, the motor will be perfectly even with the hole now. I am looking at 4' of horizontal duct and 1 90 degree bend to get outside.
Finished board on window:
Total cost today: $0 (already had all the materials on hand)
The company I work for was also in the process of clearing out the warehouse so I also picked up 2 massive 4 feet by 3 feet shelves to put in the garage. I can stack finished pieces or park items that are about to go into the kiln. The shelves on the ones I picked up are wood but I can always put a small piece of sheet metal over the ones I want to "park" on.