Help me choose a deck core material

[pescaloco]

Guys I want to make and install a cockpit deck on my boat
It is a 12 foot X9.5 wide area

Would like to use Vinylester resin and hand lay up
There are no build plans and no old deck to duplicate as this is a new custom

I can use ply but was wonder what opinions would be on Balsa core or Nida Core

I have a large unsupported span and will also need to make a large engine access hatch
inboard disel

Any input on core material / Core thickness / Lamination schedule would be much appreciated

Thank you