My son-in-law Tim had some 20 mm thick monopan left over after he built a caravan.
He cut two 800 mm diameter circles for the base of my GSO 16" and the scope is now 8 kg lighter.
It also rotates better, its very smooth.
The rest of the base is still the same.
Monopan 20 mm thick can support a weight of 380kg/m2
http://www.monopan.ca/about/