The link explains how they were all made. They were all 12mm panels. Your point about thickness is salient though. If ultralight is indeed the same weight as 1/2", but comes in 3/4" then if the parts can be made to fit it should produce a much more rigid panel without increasing weight. This is because deflection is mostly correspondent to the height of the material along the axis the force is being exerted upon (think about how ceiling joists are often made with 2x12s or 2x10s, all the rigidity is in the height, not the width).