here's mine. https://pbase.com/bobfriedman/image/161259960
That's an impressive setup!
Mine is similar looking, I use a large Newport SG Honeycomb board and my setup is vertical, using thorlabs' 95mm optical rail, XT95B-600 to be exact. I don't use speedlights.
I rebuild put mine into a horizontal setup in 5 minutes, that orientation is usually used for experiments for my job.
I'd suggest SM2 tubes, the SM2 collar, and a cheap long arca-swiss rail for the tubing, allows centre of gravity to be placed in the middle instead of at the back. You will have to flock the tubes yourself. I roll flocking adhesives and put them in, simple.
Goniometers are nice, I have a dozen of those but have yet to incorporate them into my setup.
I also see a polariser, presumably it goes in front of the objective? For objectives, that's not a good idea. Get some cheap film, cut them, and tape one to the back of the objevtive adapter; also polarise the lights.
Rotating the polariser is going to be difficult, this should work nicely (attachment).
Just use double sided tape and put it onto the cover, allows rotation. I have one of these for the SB-910 speedlights I used to own.
One major annoyance of such a large setup is dust. Even though mine is used daily, dust builds up. I'm going to order a cover from China when I can be bothered or get too annoyed with cleaning weekly.
