I am not sure the max you can mill a stock head but I have a head on my stock bike that is milled .60ths but it has also been redomed I have about 145psi on each cyl unported virgin but if I am not mistakin I think anything over .40 has to be redomed I like the stock cut head it kinda looks like a sleeper untell u know what to look for on a cut head hope this helps also I am about 900 feet above sea level