the spacers that Bestem has been shipping with their kit were cut for the 400, not the 650.I have mounted 2 top boxes on my 400 and they were both "dead level"..!!
I think that maybe you mounted that plate backwards (If possible!) or the spacers are reversed from the one that go in the rear with the ones that go in the front.....UNDER THE MOUNTING PLATE..!! If the plate was not level to begin with - the box is going to DROOP............!!!!!!!
The folks at Bestem are working on hopefully providing the right size spacers for 650 owners, in the meantime this is what I would recommend for spacer heights:
My recommendations for the frame spacers are as follows at a minimum:
My spacer measurements came out to:
Two rear.......: 1 5/8 inches each
Single front...: 2 1/4 inches