Hi,
I replaced my rear main seal with a split lip neoprene item, and used felpro stock gasket for the pan. The result was a leak around the starter area of the pan rail. Admittedly, I am running Synthetic oil, as so many of us are. I had no problems for about 8 months, then the leaks started. I think the synthetic may have been an issue, but it would take lab testing to verify this. Anyway, keeping the oil level lower seems to slow the leak. These are my experiences. What happens in your field may be different. Good luck!