[UPDATE]
Last week-end I got the Yakima kit + Yakim strapthangs. Results: simply f... amazing!!
Mounted on my tiny Chevy Aveo a 200Lt boards + 430 mast + boom and sail; all over the roof and in 10 sec used the straps to firmly everything on my roof.
No sands in the car (well not a lot anymore), no pain, no dangerous mast going back and forward on my back seat (like Final Destination movie ...)
Wife happy as we can take our dog with us now and me happy as I take 5 mins to put everything on the rack.
Of course they are tested for 50 mph, no more (the strapthangs) but consider that in this british colony (Bermuda) where I live now the speed limit is 35 ... so no worry to lose your board or you sail.
Really satisfied!
I am not sure it will fit two boards .. as soon as I will get another one I will let you know.