[MeatPuppwt]

Getting ready to make a bookshelf for a friend and because of the design I thought up I need shelves that will be very stiff and light. Remember reading something about torsion boxes and was wondering if anyone had any experience with them. Can I use solid wood in them or is plywood recommended? Any tips would be appreciated.
Thanks

 

[MeatPuppwt]

Figured I might at well post the design so you can see why I need them or to offer other suggestions. Design was drafted out in Google Sketch-Up