Hi Natalie -

Congrats on living your dream! I am too.

3" strips would make handling the core as you lay it in easier, I'd think., but you don't *have to* do it that way. If you made sure to get resin/glass between the strips as you laid them in, it would also significantly increase the strength of the deck (think lots of I-beams, 3" apart, under the top skin, if you did it that way).

Looking forward to seeing some pictures.