I have the little shimmy at 50ish MPH as well. It has been driving me crazy.
I have brand new 33x10.5x15 BFG AT's on and have had them balanced several times. Didn't work. So I then had them road forced balanced and that still didn't get rid of the shimmy.
Now, the ujoints on my front axles do make a funny sound (not sure how to describe) when I move forward or reverse with the wheel turned to lock in either direction. Not sure if it is both of them or just the one. There isn't any slack or wobble in them that I can tell with my limited experience of ujoints.
About this tow-out, I have always heard to have 1/4" tow-in. What is the difference and how will that stop the shimmy? (I am not questioning your wisdom, just trying to understand it) I will try this 1/16" tow-out soon and let everyone know if it helped.