Dwight is describing a Shadow Box dio which is the best way to cause a forced perspective.
These are usually done with a front cut out of the box and some lighting inside the box to show the scene. The scale difference between 72nd and 1/100 is pretty large so a shadow box would be the best way to do this. What part is in 72nd? a PT boat?
Of course, you can just build it for yourself and then it doesn't matter as long as you like the results. A lot of us seem to have a hard time doing that anymore.
Can't wait to see the pics and if you want more info on shadow box diorama's you can check out Shep Paine's How to build Diorama's that Kalmbach carries (hey, that's a shameless plug for them, where are my royalties?).