So I have the part #'s for the stock inner and outer felling dawg upgrades from Stihl for those 2 saws. Luckily they are the same part #'s. # 1135 664 0501 and # 1135 664 0500. I would like to stay stock for these to saws. Going much bigger would suck up too much bar on a 20" My local Stihl...