The announcement letter from Keystone about the Andersen hitch (and others) voiding the frame warranty is here:
https://www.montanaowners.com/forums...ad.php?t=83693 Post #1
There was a subsequent letter from the Andersen folks saying that if Keystone denies a warranty claim and it is proven that the Andersen Hitch caused the problem they will pay for repairs. That letter came be found here:
https://www.montanaowners.com/forums...ad.php?t=83697 Post #1)
The question is how much time and effort are you willing to expend should a frame problem occur?