The manufacturers of RV and trailer covers now are designing most covers to be used with rooftop AC units, since they're almost standard equipment these days; I suspect the cargo rack is shorter than or the same height as the AC unit, so this shouldn't affect the fit of the cover.
With that said, I wasn't able to locate the exact dimensions of a 2004 Arctic Fox 1150 but previous models I've seen are around 19 feet long. For this reason the Camco UltraGuard Slide-In Camper Cover - 19-1/2'... view full answer...
The # CAM45770 is going to be a little loose as you said and would be the cover to get if you had the 992. What you need instead is the # CAM45771. This is confirmed to fit your 2022 Arctic Fox 811. view full answer...
Since your 2013 Arctic Fox 990 is 19' long, the 19-1/2' Long Camco UltraGuard Slide-In Camper Cover # CAM45773 is the perfect solution for you. These are pretty straightforward and have straps to help tailor the fit to your liking.
Please note that the corners of campers can tear any cover if you aren't careful. We recommend covering any sharp or pointed corners with pool noodles or something of that nature to help prevent damaging the cover. view full answer...