Ms261cm. 20" bar to big?

[Stihl 041S]

From the Stihl website:
STIHL recommends #3634 (26 RM3 67) OILOMATIC® Saw chain and 16" 3003 008 6813 Ematic™ guide bar combination.
Works fine for me. YMMV. Also, a 16" chain has fewer cutters and rakers to sharpen & adjust. Also, 16" on the MS261 is about all I want to bury in an oak stump.

Different stihl literature has different bar recommendations, they are not set in stone

And fewer teeth means they get dull quicker. So you have to sharpen more often
IT’s physics