A lot has to do with what you are going to do. I will all ways try keep my truck sanction legal so if I do race it and with a header tank it would not be so. Now I am not sure a Perry pump would be either. I know the mid tanks are and going to the 125cc tanks is but going to a smaller tank when racing means more pit stops. When going to a mid tank you put the tank where the radio box goes so you have to relocate and make brackets for servos and radio equipment.