imho...the best git rot...is to git another board !
It only works if you can completely dry the wood first.That is about impossible on most transoms.
Rot is a fungus that never stops.....![]()
What if you had a building you could put the wood in during the summer months out of the weather? Would it dry out enough in that hot dry environment to make a difference, particularly plywood?
easer and faster to replace