i don't have an 18R-G, and have no hope in hell of getting one, certainly not as cheap as a 22r anyway. i am right in presuming that 18r-g pistons have big domes to get compression right? that's why i need to pump lots into a smaller combustion chamber. why can't it be done? do they have different water holes, different oil holes or different head bolt location or what? is it possible to overcome the problem??????