When I worked with Corian,and similar, worktops we dreaded having to lift them once a sink cutout was in place.They were prone to cracking or even breaking from the corners of the cutout to the edges.We made a point of carefully sliding a similarly sized piece of plywood or MDF under them.I would think you ought to be providing a lot of support to a sheet of that size as objects of any significant weight may cause deflection.For aeromodelling,it may not be a consideration.