I'm starting to sketch out ideas for a set for Seussical this fall.  I'd like to place two platforms off the corners of the stage... that is, one corner on the stage next to the stairs and three corners that are over the floor level.  The platforms would cover the stairs (I'll be building two ramps to allow stage access).

The challenging bit is this- the platforms will be fronted with some translucent material and will be internally lit by an LED light fixture during the show.  That means I can have NO internal bracing that would cast shadows.  Theoretically, that means I could have bracing across the back and sides of the platform, but nothing across the front where the light would be aimed (short of maybe one crossbeam across the bottom of the front to keep the front legs from walking).

I've read suggestions to use L-shaped legs for stability and strength and a piece of plywood to join the legs to the platform frame.  Would this be better than using square columns (like fence post material) and bolting them directly to the frame?

Oh, and the other restriction is that I don't know if I can anchor anything to the stage itself.  Any thoughts?  Originally I wanted to use scaffolding, but nobody in our group has access to scaffolding.

Can you talk a little more about the shell construction?  A quick Google search didn't turn up anything.

I'm not terribly worried about sight lines.  The first row of chairs is rarely filled anyway, and I'm mainly extending the stage to the left and right (only slightly forward).