A lot will have to do with how dirty the rinse oil is after 3500 miles. If it is black, then we will have to assume some additional cleaning is necessary. If it looks average or good for a conventional oil, then perhaps the motor still needs some run time on conventional mineral oil to help the polymer seal shrink down on the crank journal. I am just checking that you did run conventional motor oil during the rinse phase. At this point it must be a very small leak, if nothing makes it to the ground. Is there a chance that the seal leak is solved, but the gunk on the back side of the motor is still flowing down on top of the exhaust, when the motor heats up? Is it possible that the valve cover gasket is seeping a bit leaking oil down from much higher above the rear main?
At this point I would run another oil change interval on just conventional oil. Unless like I mentioned the rinse oil in the motor now is very dirty.
