3/8" ply under 1/2" foamboard; is this ok?

[MasonJar]

2" extruded foamboard on its own would also be plenty strong on risers with 12" spacing. We use it with 24" spacing for our modules at <!-- m --><a class="postlink" href="http://www.hotrak.ca">http://www.hotrak.ca</a><!-- m --> and it is very easy to work with. Lightweight is important when you are assembling and dismantling a ~50'x~25' layout every six weeks.


Andrew