thanks a bunch.
i'm thinking of combining the RRO adventure rack with a thule boxter right now.
That a nice aerodynamic roof box. Bear in mind that, unlike the factory cross bars which can be adjusted front to back, the RRO cross bar locations are fixed. These might not align with the Thule's mount locations. It's still doable if you don't mind drilling a few new holes in your expensive Thule and concocting your own mounts (u-bolts or pipe straps or whatever).