A good point. To quote Freidman:
"All structure above the gallery deck would be removed, and a new strength deck,the new upper deck, built at the gallery deck level."
Ahh of course. They knew what they were doing! It makes a lot of sense to lower the deck to improve stability. You should keep drawing the cut down light carrier. Make for an interesting comparision to the American light carriers made from converting the Cleveland class cruiser.