Since my newly built trailer is the only thing I have that can haul full sheets of plywood, I want to get it all in one trip. While my trailer is still a flatbed...

I'm building the Generic Benroy 5 x 8.
*** How many Lauan 1/8" sheets will I need for the inside and outside ceiling and hatch? ***
I'm thinking 5, but is it 6?
Thanks,
-phil