Core thickness of deck on 78 MA

[Capecafe]

I wanted to see if anyone could tell me the thickness of the core material used on the deck of a 78 Master Angler? I've already re-cored the deck lid over the fuel tank and used 1/2" Penske board with a full cover of 1708 on bottom and top, and it seemed to fit perfectly, but I don't want to assume the rest of the deck is the same. I'll be using Penske or Coosa and would like to pick up my materials before cutting off the deck skin. Any help is appreciated.