Built up how? I have two SX-1's that Bob upgraded and tuned up for me, but they still look like stock guns as I kept them blued and did not go for any of the metalic finishes (metalite?) that Bob was fond of.
I did start an SX-1 custom gun project based on conversations with Bob who unfortunately passed before the gun was finished. Many on this site have seen the gun, but pics are below. In this case, with Bob gone I had my friend and excellent gunsmith, Ernest Marlette, do the smithing.