Murox
Queen Bee
Yes i think you are correct - I have not used a national for many years and I do not recall ever seeing any internal battens in the roof - probably a matchstick lobbyists invention.They certainly are not necessary, as has been said previously they add minimal structural strength. As I said flippantly earlier I am of the opinion that they are there purely to allow the air to circulate within this void and allow air to rise through the Porter bee escapes and exit via the meshed vents.
My roofs are constructed using 150 x 15 cedar screwed and glued onto 12mm ply or OSB with no battens. I've never had one break yet.