Looking for some help on an older IH 496 disk........25' wide and 9" spacing........and it is a rock-flex. We are looking to replace at least the front blades as they are in pretty tough shape. They measure anywhere from 17" to 19".......Someone must have had it apart and only replaced a few blades. The rear blades are in good shape and measure about 20" pretty consistently. The question I have is with what diameter should we replace the fronts.........how much clearance should there be between the edge of the blade and the rectangle tube frame? According to the part numbers on the existing blades......it looks like they were 22". I did some measuring and if I put 22" back on it, there will be only an inch or so of clearance between the edge of the blade and the rectangle tube frame above them. I can also see where the rock flex allowed the old blades to rub a few spots.....mainly on the brackets that hold the rock flex standards to the frame. My dealer is telling me to use 22"..........I am wondering if I should put 20" to help with the clearance issue.