I tested a range of apertures (f/2-f/8) to examine the quality of the IR hot spots I mentioned in my last post.
As you can see in the images below, the hot spots are present even wide open (as a loosely defined shift in color and brightness in the center of the frame) and become more defined as the aperture gets smaller.
Though diffuse, the color shift is visible even at f/2. (Saturation pushed to 100% in Lightroom to help illustrate spots)
Spots are becoming more defined. (Saturation pushed to 100% in Lightroom to help illustrate spots)
From my limited experience so far, the spots are likely to have little impact on B&W shooters as a simple desaturation seems to eliminate the artifacts in many instances.
Desaturation greatly reduces the artifacts and makes post cleanup much easier.
If left in color, the distribution, shape and variance in color across the spots make them challenging to remove in post. The X100T/R72 combo is not well suited to false color work to begin with (not sensitive enough to the visible spectrum to register usable variations in color) so I don't see many people running into this, but I feel I should mention it nonetheless.
Hot spots can apparently be caused by reflections inside the lens barrel. Typically the interiors are designed to prevent visible reflections but don't take IR into account. There is a possibility that the filter adapter I'm using (cheap JJC) is contributing to the effect, I will try to find a way to test that and see if anything changes.