Spectacular! Need a couple degrees of straightening or perhaps some distortion control..not sure which but something is just a touch off.
I'm not sure what you mean by '32 bit channel'. Do you mean you were merging several exposures in PS rather than in photomatix?
I think it is a marvelous shot! Also very difficult to frame it in the camera and then have somebody measure it on their computer.
If it needs any straightening at all, it might be due to your camera position not being exactly in the center when you took it.
I've seen something like this before (it may have been a church?) where the camera position was just off by a mere smidgen, causing some slight differences most notably at the perimeter.
I do like it.
Thank you for your Support! Very Difficult to straighten!!