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