What Thickness do you use for the Top & Bottom boards?

Hi all,

I've just finished Dulcimer #3, scratch-built to my own design. This instrument has a body made from Douglas Fir (it smells absolutely beautiful - almost like oranges!) with a Beech neck and Ash binding. I'm very pleased with it - by far the best sounding, looking (and smelling) instrument I've built so far.

However, I'm already looking to move onto build #4...

Now my question is this - what thickness do you use for your top and bottom boards?

Dulcimer #1 was 3mm thick plywood top and bottom

Dulcimer #2 was 3mm thick pine top and 3mm plywood bottom

Dulcimer #3 is 2mm thick top and 3mm thick bottom Douglas Fir.

Do these dimensions sound too thin? Too thick? #4 will most likely be Douglas Fir again, although if I can find some Mahogany / Spruce, I'd love to try that!

Thanks 

Tim