if yer running .325 a 550 will run a 20" all day long no problem. judging by the way mine pulls a 16" 3/8's i wouldn't hesitate to try a 20" 3/8's and use it that way once in a while but i only need it to run a 16" as i have other saws to run longer bars. she flat out rips with a 16" 3/8's. almost have myself convinced to send the 346 on it's way.