Total valve lift has nothing to do with the possibility of pistons hitting the valves. If they clear with 1.6 rockers, 95% of the times they will clear with 1.7 or 1.72 rockers. It's the overlap period (exhaust to intake cycles changeover) when both valves are partially open at the same that PtV can occur.... like the sample shown below.
Thanks for the answers. I understand the theory but also understand how it can happen. Higher lift can mean faster ramp up, aka, more open at a given point in the cycle which could mean ptv problem. Thanks again for both answers!