Kenny, I have not built ILF longbow limbs.The drawings above would be for longbow and recurve limbs. There dosen't seem to be a true ILF standard but I think alot guys use the drawings I posted. I have 7 ILF risers from 4 different manufactures and the 2.3125" center to center varies in some of them. So does the ear length,you dont want the end of the limb rubbing against the riser. I really like Aluminum risers with removable grips.