I really like the .325 on my 50cc and under. Runs really smooth. Keep it sharp and out of the dirt. Don't know about the rim. I don't bother swapping that stuff. I just swap saws. Sent from my Moto E (4) using Tapatalk
I run 3/8 72dl full comp on my 550. I really only use the 550 to log cedar and to limb spruce and balsam on the header. I have blocked firewood with it also. It handles it just fine in my opinion. I think it’d like a full skip better. Which I will be switching to once I get around to spinning up a loop.
As far as best, it's personal preference IMO. I like the 16 on mine too. 3/8 on everything is just easier.