I'm making my own homemade, big bug box and would like to know opinions on the "best" foam (and supplier) to use in a homemade box?

I measured the foam in my Cliff Box (i.e. The Beast Jr.) to be about 7-8 mm (By the way, I love my Cliff Box!)

I'll slit the foam myself, but I'd also like to know opinions on whether to "slit" like in Cliff Boxes or to "slit and punch holes" like in some other brands.

Shannon over at Texas Fly Reports has been doing some box building and might have some useful info.

That's my best.

BTW, thank you for all your great photos and articles!

I make my own fly boxes for large flies. I use a 6mm foam. A good supplier:
http://craftsuppliesforless.com/kidscraftsupplies_foamsheets2.htm

i just used the really nice waterproof plano box and foam from Micheals craft store and gorilla glue.