A printable frame is now included in the frame subdirectory of the Git repo (OpenSCAD source and STL included).  It's assembled mostly with M3x12 screws and nuts (had to step up to M3x16 for the vertical connections between frames) and can be extended as far as you need to go.  It accommodates both v1 and v2 boards (probably a capability only I will need, unless someone else built v1 that I don't know about).