Use blast gates with a dust extraction set up to shut off the air flow to lines that are not required, therefore maximising the airflow from the line that is needed. Hard plastic blast gate outlets are 4" (100mm).
For those wishing to know the internal and external dimensions for connecting to existing machines or other setups. 98mm to 102mm taper making it ideal for 4" hose.
Remember to always have at least one line open at all times and position the blast gate so it slides sideways, rather than up and down, so the vibrations do not close it during use.