Ray:
Here's two documents that might help.
First one is installation instructions for a Reese round bar.
http://www.reeseproducts.com/support...fs/65509IN.pdf
What's missing in the above instructions is any mention of ballmount angle. This second document (although about trunnion style) does at least discuss the angle and usie of the the washers to adjust it.
http://www.reeseproducts.com/support...fs/66006IN.pdf
I don't know much about the Reese, but hopefully these will help. It sure seems intuitively obvious to me that adjusting ballmount angle & possibly height should help you get rid of the groan and still keep everything reasonably level.
Ed