The "Hull-a-Port Pro 837" from Thule was actually developed as a canoe carrier, but is also excellent for towing bulky SUPs and does not spread out on the roof.
With two boards on top of each other and one board on edge, you can easily get up to three boards on the roof. It is also particularly suitable for race SUPs with a round underwater hull, which are difficult to stack. When unloaded, the brackets can be folded away in a single aerodynamically optimised movement. The accessories include sturdy straps with padded buckles, the bracket fits on conventional load carriers.
Price: 169 euros.
Info under www.thule.de
Fits on conventional load carriers.
The brackets can be folded away aerodynamically.