Spanish "wood" isn't much cop however it's stacked, ply and timber seem to be some close b@stard relative of balsa, warps like billyho, and is only suitable for making Robin Hoods bow. Plywood, (madera contrachapada), bends before your very eyes, to see it in a twisted stack in the bricolage is a sight to behold. Timber lengths have to be unscrewed out of the rack, I needed some 9mm x 9mm last week and left without buying any such was it's warp factor.
Aluminium would seem to be the way to go, but I'm not at all confident of it's dimensional stability as a baseboard in these climaes.
Tim Horn will be getting my contract.
Mike.