Hi Keith,
This is a very interesting idea. I think for those of us trying to stuff a lot more tire, this would make sense to do but saving the other side of the frame rail. This would put the spring more toward the inside of the frame, as opposed to the outside like you have it now.
Secondarily, it seems like this would maintain a lot more of the structural aspects of the frame.
Are there any down sides to keeping one "side" of the frame rail like this?