2 part Magnum cam and valve spring question

I have the Hughes 1110 also with the retainers that will allow more lift. I had stock retainers and springs/ My camshaft lift was 498/512 and when I had it assembled with the stock stuff I had about 15-20 thousandths clearance which was a little close for me. The Hughes retainers and springs allow up to 550 lift and and with their retainers they CLAIM that there is enuff clearance for a 600 lift cam.