Panel sizes for cyrstaline marble?

I am having a discussion with an architect, regarding acceptable panel sizes in 20mm thick marble, which is to be fixed on a steel structure. He wishes to use panels ranging in size from 2700 x 1200. Some of these panels are to be placed COP both on an internal face of the curve as well as the external face. I will refer him to the relevant standards listed on the ASAA webpage but I’m hoping for some useful dialogue from other industry members. I believe that even if he halves these stones, there could be some issues with the panels’ stability as well as the location of fixing points. We are also discussing the joint spaces required, to allow for movement in the steel structure. Pieter Boer (member)