Update ...

I have passed along my design for a six-sided tube to my wood-working friend from church.  It will be 5" on a side, made from 9 mm (3/8") panels with longitudinal supports on the corners for strength.  It will have a minimum of 8" internal diameter which will provide for the 1" minimum clearance around my mirror.

Preliminary design indicates a tube length of 67" (see the "Newt on the Web" data sheets for details); so I will ask for 69-72" long and trim to fit after verifying the placement of the mirrors.  Easier to make it shorter than the other way around ...

My friend will first construct a much shorter (couple of inches long) 'mock-up' as a proof of concept of the design.  He thought it would be ready by Sunday; no real rush as until the materials I ordered from the States are in hand, the tube, primary cell and secondary holder are pretty much the only parts that can be built for now ... everything else (including the final length of the tube) depend upon the final placement of the hardware, including the focuser and eyepieces.

Just for giggles, I've been playing around with "SketchUp" a 3D drawing tool that helps put things into perspective.  Below you can see a 69" tube with a 6" mirror ...