Silly question

Are you absolutely sure the leak is from the rear main and not a galley or cam plug ? Had a customer several years back in a similar situation. he had done 4 or 5 pan gaskets, a new pan, and 3 rear main seals.
He brought it in to us totally frustrated.
It turned out to be the LR block plug (galley access) was loose and dripping down making him think it was the rear main.
We thoroughly brake cleaned the back of the block through the inspection cover, let it dry, fired the motor up and within a short period the leak appeared. We shut the motor off. Using a pair of mechanical fingers with a small paper towel I snaked it up into the bell housing staying away from the rear main. When we removed it it was wet with oil. HMMM, Oil doesn't run uphill
We dropped the trans, sealed and tightened the plug and it has never leaked a drop since. (12 years ago)

Keep us posted