i glued on the stiffener before i cut the doors. the door fit pretty well, but despite the fact that i was fighting the idea of using the strap contraption, i decided to give in and try it. on another thread, someone suggested using a “backpack clip” so you can properly tension the strap, since it would be virtually impossible to get the right tension on it while you’re trying to screw it in under the fairleads. i did that, and after tweaking the tension, the door fits perfectly. you might try that before cutting into your stiffener. i also had to use a few washers under the bottom fairlead on both doors to get the bottom rod inboard enough so it wouldn’t hit on the bottom of the door sill. finally, i thought the 7/16 thick foam gasket supplied by CLC was too thick, so i used 5/16 thick from the hardware store.
if you have an REI nearby, they stock replacement clips for $3.50. they are displayed where the backpacks are.