The concept of the Sims device is a perfectly sensible one and can't imagine it not working.
However, I agree with most here in that what you shelled out for a "custom" should get you a lot better than 1" with a #5 Shilen. I'd definitely think getting the rifle looked at by a good, reputable gunsmith and rebedded would do you wonders. A custom rifle that you spent 1 or 2 grand shoudn't need that. Maybe full length bedding or just a pressure point would help.
