Yeah so just power her on, I would suggest might as well test your PC connection or whatever this bad boy is going to run, and then rotate the monitor on it's side - Look for discoloration. Try both directions because sometimes, depending on the set and where we are located on the globe, only one direction will be a problem.
You can solve by either making a degaussing coil or buying one of those green wands from amazon or ali-express, but they are not very strong.
The situation here is that it may come back while rotated no matter what you do - I've been experiencing this with one of my sony sets and it seems like the mask is just magnetized anytime the set is on while in vertical mode. I first wondered if one of the color drive chips were bad, and what I ended up doing in my troubleshooting was trying to ACTIVELY COOL the chassis board with a fan in my candy cab. I don't think the temperature was the problem, but one side effect i noticed is that as long as there is a fan (AC powered, desk fan, clip fan, etc) in the cabinet, I believe the rotor of the fan is acting like an electro magnet and it keeps my screen completely clear!
Like I said, I had 2 sony sets, higher end consumer, not pvm/bvm and they both seemed to experience this. The trinitron, no matter what I do will always discolor when rotated, the wega seemed to do it only when power was on to the monitor.
so what I'm trying to say is - test it out, with the set on/off and maybe everything will be fine and no issue. If there is an issue, you can try to solve the issue with magnets, coils, wands IF AND ONLY IF the degaussing circuit doesn't solve it. If for some reason these sets are similar, you can try to put a fan near the set and see if it prevents the issue. Freaking voodoo man, I swear.
If it does discolor when you rotate, turn it off and back on to trigger the coil on the monitor and see if that solves the problem first, which it probably will.
Sorry to ramble so much about this issue but I wanted to offer some additional detail and hopefully save you a headache. I hope it works just fine, or worse case you turn the tv off when you rotate. Crossing my fingers for you.
Also, I think this build looks super over the top and BADASS and I can't wait to see some more progress. This is freaking cool!
Daniel