I was tightening the lock washer on the drain from underneath the sink and when it felt tight, I stopped. Looking at the drain from on top, there is a gap, indicating I still need to tighten it. There is a rubber grommet on the drain to stop leaks. It doesn't leak but I'm afraid to tighten it anymore. Could I crack the sink? Should I have a helper press down on the drain while I tighten it? The sink is a quartz, to match the new granite counter tops. Thanks.