Thanks 4 jaw,
You make some very valid points. The "watts" link system is very good at limiting side to side movement if properly mounted. It will work in a confined space too. All of my stuff is TIG welded because that is what I do best so that is a given.
Bottom line is make it tougher than you think is necessary then add a little more.
With all of the high power crate motors and big tires available now, it requires a very tough rear end and mounting to survive "over the road" use.
thanks for the comments.