Was searching for the same solution. Don't want to waste a perfectly good Thule box. Confirming you just installed upside down from what's pictured on the Amazon photo? Using just the main bar from the original rack? Any photo of yours available?Quick note: I have a Thule Motion XT XL and use this to attach it to my Leitner ACS rack:
WILDROAD Universal Roof Rack U-Bolt, Upgraded 2 PCS Cargo Rack U Bolts, Replacement Hardware Mounting Kit for Roof Rack and Roof PlatformWILDROAD Universal Roof Rack U-Bolt, Upgraded 2 PCS Cargo Rack U Bolts, Replacement Hardware Mounting Kit for Roof Rack and Roof Platform
I omitted the large plastic pieces. Each kit comes with a pair. Need two kits.