Step #1 - roof survey. I have a few 145" 1515 rails on hand. We use them vertically to launch high power model rockets. Put one in position on the roof to evaluate length... overhangs a little in the front. So, will have to cut a bit off, but still be happy with one piece side rails. Ordered 4 pair of Hein's excellent Promaster Roof Rail Attachment and L Bracket adapters. Once they are installed, I can determine the length of the crossbars and have them cut as well. I want to work on the roof using a platform on the rack to avoid any damage to the sheet metal from my stepping on it.