I don't have any personal tech experience with these cams but from research I've found that .550 lift is probably the limit for a PI head. Not sure about the NPI though. I would think it would be since the lift for the all of the Comp cams in an NPI head are .500. You would think that they had researched it to get the best performance possible without causing failures.
If the Stage 2 has that much lift I'd think you would have issue right away.
In a short answer the VT cam will not work in a NPI head. Anything larger than .545 lift, the correct lift for the PI Comp cams is too much for a stock NPI head. You will require Crower offset retainers, good springs and some other things to make a cam with more lift than .545 work in a NPI head.