Hi Alan
On most jobs i have my porty truckmounted,using 250 to 300 psi with a 100 ft of hose with excellent results and could use up to 150 ft without losing noticable loss of waterlift and airflow.The booster box is a very good piece of kit, but i believe should not be used when useing less than 50ft of hose with powerful porty's.
cheers mark