shop foreman payplans

i just inherited a shop that has 34 techs and 2 foremen,the previous manager was paying the foremen a flat monthly salary.I want to change them to a performance based plans so they can make more or maybe less monies depending on how well they perform.We will going to our new facility in a few months and will be adding 12 more techs.Does anyone have any plans that are working good for them ?? I was thinking something for frh and a bonus for CSI but im not sure..any help is appreciated