A couple of alternatives to the rhino vortex bars are available so figured I’d mention it.
I ended up going with Gamiviti feet and FrontRunner bars. I recently picked up a Thule Motion 3 XL box for our Sienna and it should fit with the 3 bars perfectly based on measurements and the clamps seem wide enough to grab onto the FrontRunner load bars (if not there are kits to mount with the T slot).
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There is also Eezi-Awn which has the added benefit of adding a mounting rail to the roof so you can adjust the bar positions.
@RockDriver I think this would also best meet your need best for fast on and off.
This kit includes (4) feet -or- legs and a load bar set, ie. two bars. Additional components can be purchased here. The K9 Load Bar System from Eezi-Awn is a revolutionary advancement in expedition-style roof management and storage; it is thinner, lighter, stronger, quieter, more functional...
www.equipt1.com