Guys ...
good wood structures, solid, laminated beams, are about 1.5-2x as strong as steel in both stiffness and strength.
By mass.
Sitka spruce is one option.

They need the high H measure for the stiffness, but mass little.

Likewise, optical tables in steel are very much stiffer / stronger than machine tool gantries.
They are very much air by volume.

Aerogels are much stronger than anything else, by mass.
Lab stuff, google it.

At some point suppliers will start to offer std beams in things like aerogel/complex web/optical table cylinder formulations for not much money.
Aircraft, trains, bridges, anything of high value and volume cost about 6$/kg.
(Sales price is different.).