Safe max lift on X heads that retainer hits seal @ .550??

I mocked up my 340 w an XE282S .520/.540 advertised lift. With the lash set @ .016/.018 and PRW 1.5 rockers witch fall shy of an actual 1.5. More like 1.45. Put a dial indicator on the valves and am only getting .483/.502 actual lift. Thats ALOT of lift lost. I may just use this cam after my curiosity surprised the hell out of me.