Just a suggestion: Why not purchase the Passat, and if the harp doesn’t fit, sell it.
My caution is that even though the wagon may fit a concert grand, the harp model does make a difference. I was able to fit one of my concert grands into a Honda Element, but my other one from a different maker would not fit. It had to be loaded onto its column rather than flat. Through the years, 23’s were manufactured in different heights. Also the geometry is different between the 23 and Atlantide.