An experiment, yet I had a platter made in Panzerholz, a replica to exact Garrard's underside, beginning from a disc weighting about 9 kilos, I obtained a disc 320 diameter where - as a plus and NOT by chance:-) - I can also use my original Shindo's 800 grams mat.
Delignit Panzerholz's very stable character allows a careful lathing to mirror-like surfaces; in the very next days I'll have platter transparent lacquered (but on inner rim for better idler-wheel spinning eveness) and polished to a super, sexy gloss.
For added precision of bearing/platter mount, I had a bronze centerpiece imbedded from underside in Panzerholz and precision balanced/machined together, a real PITA to execute it properly!
Platter looks perfectly balanced to "usual" 0,02 mm tolerances and inner rim where idler-wheel runs is smooth and precision lathed like my (beloved) bronze Garrardzilla's monster platter.
Weight is about 3,5 kilos.
Sonically... well, I'm right now beginning first listening tests.
Will keep you informed.
Caution - do not try this with lesser plywoods, as it can be VERY dangerous - i.e. separating plywood layers, debrises and other harmful eveniences... Delignit's Panzerholz - beside the cool brand-name - is an expensive, made to high standards material and a completely different breed, which makes it suitable also for such a weird use.