Another follow-up. I conducted the test again with Ilford MGWT, but with the vanes fully closed. As before, I am using the yellow tape filter in the bottom, which contains 3407 and 3406 Rosco filters, and a red tape filter in the vanes containing a sheet of #19 Fire.

No fogging after 7 minutes. With the vanes open I had fogging at the 3 minute mark.

I extended the test to 3, 9, and 21 minutes, 3x the original test. Vanes still fully closed.

No fogging at all.