B Harrison
ArboristSite Guru
Funny, ask about a 20" bar on an ms290, and most on here will say its too much for a 290.
I have a 290 with a 20" running .325 full skip. In hardwood bigger than 15" it cuts better than full comp on that saw. Results should be similar with 3/8. Haven't tried it, but semi-skip should work fine too.
If I was going to run a 290 and if it was going to have a 20" bar I would run full skip!