Hi David

I'm having a hard time picturing what you are describing but do you know how
many psi you are talking about in compression?  If you know that you can go
to Diab-Barracuda to check the compressive strength of the cores for
Divinycell.  If it's a concern, balsa will give you a pretty awesome amount
of compressive strength and modulus.  You can also taylor the compressive
strength  by varing the density of the balsa.  For very high loads, under
bolted on fittings for example, I've switched from the common denities like 8
lb/ cu. ft. to 12 lbs.  For low loads, I've used 4-5 lb density in balsa.  
This has a higher compressive strength than foam and outwardly is lighter in
density but can sometimes end up weighing more due to resin absorbtion.  This
can be largely mitigated by using AL600 coated balsa from Baltec which
precoats the balsa to limit resin absorbtion.  Be aware however that if you
sand the balsa, you will need to recoat the balsa with a "hot coat" to limit
resin absorbtion later which can starve the interface and lead to poor
adhesion.

For really high load stuff you can use end grain cedar (24 lb/cu ft) or fir
(33 lb/cu ft) for core.  End grain will withstand compression MUCH better
than grain running lengthwise since wood is like unidirectional composite.  
It is afterall a natural composite (cellulose reinforced lignin).

Dan Newland

Super ES