Larry and Dan are probably right. As you can see in this pic

sidesail.png

they've already trimmed off all the flange material at the front before they made the measurement. The manual doesn't say you have to trim it all the way down, but other pieces won't fit when it comes time to mount the front body pieces if it's not completely removed.

It was still pretty tight on my car, and I had to trim the side sail a tiny bit where it hit the welded flange to get the rear panels square.

BTW, in order to give myself a little more adjust-ability, I mounted the side sails with 10-24 rivnuts instead of the recommended rivets. The tiny bit of wiggle room it provided made it much easier to square things in the rear. I loosened the 10-24 screws, squared it all up, then tightened them down again.