Re: 20" 300WM
If you are hunting in timber, you'll want short. I hunt with a 21" .30-06 and I'm going to cut it back more because the end is ported and I don't like the ports. It kicks pretty good, but that's life. Get a limb-saver pad, and a brake if it's that bad.
Short isn't new, but you guys can't expect everyone to know that. Don't be too harsh on the new guy, everyone starts somewhere. That said, I'd suggest you just let it go rack. Nobody is quite a wealth of info if you can get past the prickly demeanor. I remember him briefly from when I was a new guy.
Just let it roll off you like water on fowl. Go cut your rifle to 22" and see how you like it, if not, cut more. Short works... besides, on a hunting rig you can compensate with different loads (even off the shelf), bullet weights, and types. WHAT are you hunting?