Ann: Quarterly Activities Report December 2014, page-9

Sure, it looks like to me the pits have a high strip ratio, as in have to move more waste which incurs a cost without cash-flow. The design relies on the ounces (grade + tonnes) at the base of the pit. The risk being higher with low-grade pits, as the economics are highly sensitive to mining factors such as ore loss/dilution or geological factors which may influence the average grade. PXG are not mining cream here, hopefully the gold price will insulate them from the aforementioned risk.