A high FC does not effect the liner as long as the FC is matched to the current CYA per the Chlorine/CYA Chart (link in my sig). The CYA not only protects the FC from the sun, but also protects the swimmers and parts of the pool from the harsh effects of the chlorine. So when a CYA is high, the FC naturally needs to be higher on the chart and visa-verse. As long as the two are balanced together, it's no problem.