First off let me say you chose a really good compressor those Eatons are excellent compressors that seem to last forever. Cut-off pressure/tank size are chosen based on expected demand with a lot of consideration given to pump efficiency vs motor power over the entire charge cycle. This is engineered at the factory and with a well built unit like an Eaton you can figure it is about the optimum set-up as is. Changing pressures, like adding tanks, is usually a mistake since it can be counter productive and increase compressor wear without gaining anything but unless you make really big changes like really huge pressure changes or adding huge tank volumes then you probably will not notice much difference. Lowering pressure will have the effect of shrinking tank size and produce more frequent but shorter run times that may not allow for proper cooling periods but in the range you are talking about I don't think it would do any harm it just would not gain anything either IMO. With most 5-6 HP two stage units 150-175 psi with a 60-80 gal tank is about right with a good balance of run vs cooling time.
Last edited by oldred; 08-22-2005 at 02:14 PM.