i have run that combo if it has a dead spot because lack of gas not spring nothing wrong with a 600 vac either i had both 600 and 750 dpp 600 only 10 off the 750 750 was used but was redone 600 was new put jets in both and small(litest) spring in the 600 ran 82 in the 750 in the spring time 80 in the summer 600 ran 80 in all time drill the back plate