dmaxx, I dont have any experience with Bender's gasket. Not sure if they are the same thickness,etc. So I cant give you a good answer on that one.
I have run my Viper with both one and two layers removed with the stock pipe, with no problems. I should point out that I do ride at higher elevations and that does make a difference.
One layer removed (center)should be no problem for your altitude with good premium fuel. The important thing to remmember when doing compression mods is to make sure your jetting is correct and dont be cheap when it comes time to by fuel! While .005" is not a huge HP gain, throttle response is improved.