I suppose the other options might is Faring/wind deflectors, but the coverage won’t be 100% and all you need is for the ends to poke out (especially if they are left open and it’ll probably whistle like a bastard… What about round section bars? cheap, more aero than square (less than an aerofoil profile though) and can they be used with bike racks and roof boxes? .
I’ve been looking at additional load carrying solutions for our new car lately, I’m generally not a fan of roof bars/racks/boxes, but it might actually suit our needs on the odd occasion and be cheaper than having a tow bar/lighting board fitted for two or three uses a year…
Plus no roof rails, I can’t help thinking it’s the feet at the fixing points might end up creating some of the noise issues too.
looking on roofbox:
Cruz Airo-bar setup can be done for ~£100 and it’s only ~£60 for the most basic square bar kit, I’m sure I can go even cheaper via gumtree/ebay if I shop about that’s not too bad if I don’t want to leave them fitted between uses, but then I am quite lazy… so there’s a chance that once on they’ll be left there for a month irritating me…
I Quite like the look of the Whispbar flushbar if I was leaving it on all the time, it seems quite neat but at ~£190 that starts cranking up the budget for an occasional use item…