Based on some dimensional help from the good folks at the RPF, along with a couple of great screen captures, I'm starting my initial design work on the Tri-Viewer.
Here is my first stab at a front view.
This does not include the thin pyramid that will be on top.
The question I struggle with now is one of side view. Are the top and bottom lips angled, or not?
For reference, the part I have highlighted in red is what I'm referring to as the "lower lip". There is a corresponding "upper lip" directly above it on the tri-viewer.
My latest theory is that the side view is like this. Flat on the bottom, angled on the top: