DIY Cap Rack questions

Im looking to build either a roof rack, or preferably just cross bars for my SnugTop Sport Hi-Liner. Its primarily for an awning, but might throw something like maxtrax up there if I ever get some. I got Thule rails installed when I bought the cap. They measure around 43in long so even with just 2 cross bars itd be doable to mount maxtrax. Id like it to be as minimalist as possible(cost, drag, garage height)

Is there a reason most racks/cross bars sit so high up? Im thinking maybe things whistle if they are too close? My initial thought was to just use one of these brackets. I havent measured it out, but the cross bar would sit pretty close to the top of the cap. Is this going to be an issue? I dont have a ton of clearance into the garage with the midrise cap so adding a rack or cross bars will be cutting it real close.


Next I would obviously need a different mounting solution, but would there be any reason I couldnt use the 80/20 3075-Black-FB or 2012-Black-FB? Too much deflection? Weight would be minimal(awning is 21#) on the end.


If I end up going with the standard 6 slot extrusion, does going with the 20-2040-Black-FB solve any deflection issues? Or would I need to go the a 10 or 15 series?


Any reason to go with a rack over 2 cross bars in my situation?