Boat Materials Thread

I have a stringer/engine mount job ahead of me and want to find out what people are using for core materials.

As a perk I was hoping to find out what materials are being used in boat for lighter weight (manufacture or repair) of stringers, transoms, etc.

So far I found
Coosa strong but not that light
Total fair
Airex
Penske
Nida Core

Glass Dave or anyone else, what materials are being used now? Or should I just stick with wood?
Thanks