0I made a call to the US distributor. Nada.
Nice! When I called I first asked about cutting down a longer bar to somewhere in the 70" range for a particular usage which is a couple of mm shorter than the RDB180 you mentioned. the response was that they didn't like their stuff to be altered because of engineering and warranty concerns.
I then asked if the extruded cross bar material was exclusive to Rhino-Rack. The customer service rep hesitantly confirmed that it wasn't. Perhaps cross bars could be found elsewhere?
The response I got to that question was "I know of no plans to sell the Grenadier specific racks/cross bars at the present time. They are currently available at the Ineos dealerships."
Asking about just purchasing the towers got me a long silence before "No.".
Great! I'd definitely be interested if we can work something out. We're in OR just north of the CA border but have a few friends in different parts of Cali where you could drop them off. Send me a PM if you can
Our intended usage is for transporting an open canoe. Canoes are generally carried upside down and can be easily strapped right to the Grenadier's roof so we never considered the cross-bars to be necessary. And then we realized that the height of the rear doors might prevent them from opening with the bow (or stern) hanging down. This wouldn't bother us for simple day use or maybe even for an overnight trip but, for longer trips where the canoe would remain atop the vehicle for days at a time, we'd need to get it up in the air a bit for easy access to the rear and better visibility out the front windscreen.
We want to be able to remove the rack in the off season so none of the grab rail mounted versions will suit. Too much work. That left the HGM-rack.at bars which I like (and is associated with
@Ingemar) or the rough-parts.com rack. Both are too low to the roof to risk a purchase. Even if the Rhino bars are still too low it should be easy to T-nut some nice white oak spacers on top or even a second piece of aluminum. Well be sure and run a bow line to the front bumper.