I know I'm crusing for a smiting, but I'm pretty sure that the setting of the first Irradiance Cache strongly effected the spacing of the red dots. I don't think that should be happening if that cache is being ignored. But I have to redo my path to these setting to be sure.

The 4096 is also about 0.5% when used as a number of random samples. My problem has been with the second IC value; it should mean a really bad allowable error. But looking at the red dots that the other parameters cause, I think it's just that the other parameters force enough samples anyway the cache max error is always satisfied until the requirement gets silly.

Whichway

[Base, low quality parameters posted above.]