I kept hearing that there is better gasket material for the door seal than what comes with the Sling (heard from Henry at Midwest Sky Sports and from Edwin at The Airplane Factory build center), so I bought some. It is 93085K485, "Water- and Weather-Resistant Foam Rubber Seal Surface Mount, Hollow, 3M Backing, 0.660" Wide, 0.450" HT, 10 ft. Length" in case you are interested. Who am I kidding? The only one looking at this will be me! In any case, 10' is perfect to make it around the opening, leaving about an inch to cut off.

Very easy to put in, and I let the doors down on it (they have been held up with a strap for the past year) and it fit perfectly. Now it is time to put the latches on the door.