In relation to your warranty issue, I can only speak in reference to my local dealer which I do part-time work for, we DO NOT void warranty over an issue like this in regards to any of these stabilizers just by having one of them on your bike.
HOWEVER, part of my seeking for the one that fit the bill for me and ALL the dynamics that go along with choosing a device to combat the nature we're discussing here was one that I thought would induce the LEAST amount of stress on the frame of my bike and NOT potentially break, crack, or fracture any metal or mounting surface where the likelihood of potentially voiding warranty would be challenged, hence I personally chose the cross-member mounted device that the Bagger Brace has in an attempt to alleviate ANY potential for such damage to possibly occur versus the side mounting devices. I personally have not witnessed nor heard of frame damage from any of these devices, but I didn't want to flirt with Murphy's Law myself, because I usually lose.
This is my own personal testimony and way of looking at it and in no way do I expect to force/persuade anyone to feel the same. Just my $.02 for whatever it's worth. But it WILL work for me.
Here is a thread that discusses alot of points regarding Stabilizers in case you've missed it:
http://www.hdforums.com/forum/showthread.php?t=268326