NEW AND IMPROVED
I remade the composite of the two TMOST corridor scans. Interestingly - VERY interestingly - my scan from the first edition did not match the proportions of blssdwlf. I took them individually into Hugin to do my elevation views and could not get the arch to be at a right angle to the wall. Instead it came out to be 15 deg. off the perpendicular. But I had no problem with blssdwlf's scan. The arch was 90 deg. to the wall and the ceiling cross panels were parallel to the arch!
So I made a new composite and this time carefully worked on my scan to match the other using the transformation/distort tool in Photoshop. The images below are the result.
Note that the camera position for each image is:
TMOSTcompArch - middle of right edge
TMOSTcompDeck - lower left corner
TMOSTcompWall - middle left edge
I ended up with a focal length of 45.3mm, or 39.34 deg. in TMOSTcompHugin.
I hope that gives you something useful to analyze.