Dumb question: Is there any worry about the partial drain on a plaster pool for winterization? The mesh cover instructions say to keep the water level at 15-18" below the top, but I'm wondering if there is any issue of that exposed plaster being damaged over time. I haven't seen any issues the last few years, but I'm wondering if I should attempt to minimize the amount of plaster exposed, or if I'm just being overly worried and crazy. Thanks!