Chris,
I noticed that when we did our gearbox.
I have never see a seal per say.
I am suspecting that there really is not any leakage there.
I would also caution you that once you have sealed it, where will the pressure from the heated internals and fluids vent through? Have you not just made a problem that did not exist?
You cant articulate a Ferret enough for the fluids to spill out I would suggest.
I honestly think you are chasing ghosts mate. perhaps it is the mariner in you that likes things to be sealed?
What say you Chris?
Is there mention of a seal in the parts book? If there isn't (save me from going downstairs please) then that is your answer.
Robin (expert with a paint roller these days)