I'm sure most of us have a problem with a lack of space, especially for those big models. I needed a new coffee table recently and spent quite a while online trying to find one with a display case under it, just for that purpose. No luck, so I bought one with a glass top with the intention of making my own.
I measured it up and ordered the perspex from TAP Plastics in the US. They have a whole series of helpful videos on how to glue, build a box, finish the edges and much, much more so I went for it. After emailing them for their recommendations, I went for 1/4" thick sides and 3/8" thick bottom. The bottom is just over 17" x 37", and it has a depth of 5 1/2" - big enough for a Staaken and a few others!
It wasn't cheap: the perspex, glue (actually a plastic weld solution), and applicator, came to $160 including UPS delivery in the US. Another $7 or so for some aluminium strip to make straps to attach it to the table.
I glued it all together yesterday, then today I routed the corners to round them off, and made up the straps. I still need to heat treat the edges to tidy them up but that can wait for now...
Very pleased with my new custom display case!

Ian