shimming has more to do with a "sweet spot" in the combustion , relating to the volume of the combustion chamber in the head button , distance from piston to glow plug (ignition source as well as the nitro) , exhaust port timimg and intake timing as well as the relation the intake/exhaust have to each other which creates the "blowdown timing" number . so ya see its not really "just" the heighth of the shimming as well as many parts of the equation , i refer to the shimming heighth in a general term because i hate getting really technical and sh!t just too much work i know what makes these engines tick and how to get what i want out if them in terms of performance


so if you are going to use 25% fuel i would recommend shimming .60-.70mm in that range , yo can even drop down to .55mm but will require some expert tuning and stuff