Paul,
I planned to secure the objects with OZ clips, and would add blocking on the sliding stile to accommodate them. I like the idea of T track, although I'd worry that the screws would have so little bite in 3/4" lumber, so machine screws/nuts and washers might have to be employed. This was suggested mostly for a short local move of a large number of objects, so as far as lids go, I'd probably make a coroplast facing that velcros into place just to add some semblance of protection and minimize wrapping time. Or maybe John Molini's hybrid crate lid for extra large pieces.

And SketchUp is proving to be a very useful tool, although I still have a long way to go to be proficient!