Shouldn't be done = not sure of the vertical strength of the receiver like you said & because it may grab an obstacle rather than slide over it (sorta like my Calmini crossmember).
+1 - When I caught my cargo box in the sand over the weekend I was scared to death that I had also bent the receiver up or down. Thankfully it didn't, but then again I wasn't resting the entire weight of my VX on it.