I can say that if the rear oil pan seal (cork, rubber, whichever one you use) is out of place you will have a HUGE oil leak.
I had three of the 3-tit rubber seals fail on me in a row. I had oil EVERYWHERE, but then again I drove the car about 70miles with the seals leaking each time (roundtrip to work).
I'd definately suspect the oil pan seal before the rear main, especially if you're using the BOP seal.
Here's a shot of one of the failed oil pan gaskets:
