I'm trying to find a cargo box (Thule or Yakima) for ski season that will fit the Rock Creek's rack, ideally without adding additional horizontal bars. I test fit a few at a local REI but because of the "loops", the box wouldn't mount correctly without being off-center (which triggered my OCD). Neither Yakima nor Thule have responded. Does anyone have one that they can measure to see if it'll fit based on this diagram?