Other thing I did was went ahead and mounted a roof box onto the "stock" roof rack.
Used this as a guide:
Using a Gun Case as a Cargo Box for Recovery Gear on Roof Rack
Basically I only need this for light duty (some tools, recovery stuff, random cargo). It's only 36". I've got a sleeping platform and other things inside I need to save room for.
Got the 36" Plano box on amazon:
Amazon.com : Plano All Weather Tactical Gun Case, 36-Inch : Sports & Outdoors
Must have got a deal because it was about $60 when I ordered.
Instead of drilling holes through the bottom, I drilled through the sides and fixed some U-bolts around the crossbars. Sealed with silicon sealant and used anti-seize lube on the hardware. Some cut up pool noodles between the hardware and crossbars. A waterproof test during yesterday's thunderstorms tells me that this thing holds up well (time will tell though).
Good enough for me for this summer. Eventually will want to build a low-profile rack to replace the stock one altogether.