Stripped the hex fill plug.

[onthefence]

Update.
Took it to the shop today

The pro first hammered an 8mm hex into the hole.
Tight fit, so the hammer he used was like a round metal rock.
(It was a smart thing I stopped and left him enough meat in the hex hole)
He then pulled on it with his long ratchet but did not try to force it.
I noticed he used short gentle tugs like a human impact wrench.
It was about feel, and he felt like it was not going to break free.
He made sure not to strip it further, and went to plan B.

Next, the pro first tried to chisel it and walk it free.
That did not work.

He then got out the Oxy and heated the fill plug area.
Note, Oxy does not make metal red hot.

After that, he returned to the ratchet,
and the plug was free very easily.
The heat really seemed to do the trick.

We changed the 6MT fluid with exactly 2 Q's of redline MTL.
I also had 2 new plugs to use.

Charged me $40. Paid him $60. Great shop.