isn't sanding out the barrel channel and using the shims redundant? i.e. if you sanded out the barrel channel so that the stock didn't touch the barrel, why do you need shims?
How much weight did that Corian add?
—The stock had a pressure point in the front of the stock barrel channel, also the top edge of the stock rubbed against the barrel after I installed the shims. I wanted complete clearance.
The piece of Corian added about 4 ounces.