take it from me, go with the sleek'er model for $450!
Its only your good bike or other equipment you're talkin about, not to mention the poor sap driving behind you when it all falls off and tears up his front end! You want something that is going to lay flush with your roof top, meaning you dont want anything that is elevated in the least bit. It puts a terrible drain on your rig, not to mention your gas mileage!
Take care and good luck, from someone who learns everything the hard way!!
Joelle