Rear main seal lesson

Never had a problem with rear main seal leaks until new 512ci stroker build. Everything went per "text book" during break-in except minor but anoying oil leaks. Cometics valve cover gaskets solved half the problem but two tries at rear seal area didn't help.
Finally decided to bite the bullet, put it back on engine stand and start disassembly.
Low & behold, a slight too much Ultra Black behind the seal in cap came out & fouled the seal area. (see pic)100_2911.JPG
As they say, a little is good but a lot isn't always better.