I have the Decolav 1201 SS sink under-mounted to my granite counter. It appears that I need a special drain as none of the ones I saw available are for sinks that are the thickness of stainless steel only. Most seem to be for sinks that are more than 1/2" thick where the drain is connected. So, anyway, I bought one and used some rubber gaskets to fit it securely to the sink, but now I see that the last inch of the water left in the bowl will not drain quickly. It drains fine until that last inch. Am I missing something?