I did some research on those Diamond J kits and I would recommend against using them if you ride your bike hard or jump. Most who used them and ran their bike hard bent the mounts. I also read that moving the a arm mounting points further away from the centerline of your bike decreases stability. Many aftermarket frames, and the new Kawi's have moved the mounts for the a arms closer together.
This is all my opinion that I gathered from my research, I am not bashing the company or the product in anyway.