Lay it out and then drill small holes 1/8" or so.. to make sure it's going to work.
plan for 3" holesaw at the corners so they have a smooth arc for the boot to curve around.
Accordion Rubber Boot Replacement
use an air pneumatic body saw. [cut off the last 3/4" of the tip of the blade so it doesn't bottom out]
buy lots of blades. you might need them.