I would look at another metal one before I'd go with something flexible. I put a rubber one on my Excursion simply because the stock one will hit the top of the garage going in and out. In about three years, the rubber is cracking down near the base from the wind pushing it around. It doesn't spend all the time outside and doesn't have a ton of miles of wind pushing up against it. I don't treat it with 303 usually, but it does get washed with soap when I wash the whole vehicle. For the roof location up there like that, I wouldn't want to go with something rubber. You won't get a very long life out of it.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR