> What I have in mind would be much like Nick has in his book. The
> difference is that I am not ripping it from plywood or fiberboard. Instead
> I have store bought fiber board strips of roughly the same dimensions as
> his proposed box beam. Sounds like you are not thrilled with Nick's method
> in general.

No, Nicks method is just fine and dandy. I just don't like particle board as a structural member.

> I understand. Will a fiber board beam reach a point where it stops sagging
> or will it continue to sag?

Are we talking oriented strand fiber board now? That's a different critter, and can work as a material for box beams. But if you are talking particle board, or even chip board, once it is resting on the floor, it will cease further sagging.