Actually, you have already answered my question. You are transitioning
from 6" hose to 4" connection right before you reach the machine. OK.

That's the best way to do it, at least for my planer and jointer. The
experts say to narrow it down right before the blast gate, if you are
using them.

My other machines are further down the line, and I narrow the trunk
down to five, and then four inches on down the line.