I picked up the Yakima FatCat 6 system a couple weeks ago and love it so far... I choose it due to the profile shape and size. I haven't found a speed where it whistles, but think I heard a light hum around 50mph. Will have to report back on noise while having boards/skis on it (waiting for a snow day).
I tested my board upside-down without the extension- works fine- binding straps had to be manipulated for the board to sit flat and they rest on the roof, but the folded bindings cleared (bulky Burton Missions). Confident I can get 4 boards on, but would want to protect the roof from the straps rubbing if driving long distance.
One thing that makes me slightly nervous is the universal mount that attaches to the 4R Sport's roofrack. It leaves the "claws" bolts exposed about .25"... Seems like the exposed bolts could be hacksawed to remove the rack and all, but still safer than previous racks I've had- Just wouldn't want to leave anything up top overnight.
Also- I was also looking at Rocky Mounts (
RockyMounts.com - ) as an option. They are newer to the rack scene and have focused on bikes, but are releasing ski/board systems this winter. Slightly cheaper than Thule and Yakima... Look to be decent and worth checking out for anyone looking...