What are you trying to accomplish with the rifle? I assume since a 20” suppressed Dasher is an option, this isn’t any kind of competition rifle, so sure, 20” makes as much sense as anything.
I have a 10” 243win and a 15” 6 creed. I had a 14” 300 wsm for a while, and had a 11” 7 BR. All of it works.