Hey AFS, over the years I have also known different types of elastomers to have different thickness readings from one end to the other. I haven't seen too much of it with natural gum rubber, but have seen it with some latex sheeting. The absolute worst as far as differing thickness on the same sheet is Linatex a latex formulation. Their quality control has to be the worst. I've had sheets that mic differences of up to .020" from one end of a 12" piece to the other! I use it to my advantage though. I just cut a regular taper but keep the thicker end of the differing rubber at the front. In effect a "Double Tapered set". You are right on though. The quality control on some of Latex distributors is severly lacking. Good post Bud.