Sadly you can't. At least as far as I know. I have heard of people using a sharpie or tap to cover it though.
As a followup, ran some stress tests with only a 1C difference on a single core between the fan as intake and the fan turned off. Ultimately, the fan is superfluous for the airflow of the rig, but it also doesn't seem to add any negative aspects. I'm sure if the pc was in a more confined space, the re-circulation of warm air would have a larger impact.
-2 on the avx offset. I haven't worried much about avx. Intel burn test gave decent enough temps with the avx offset.
It's not delidded, but doing so is tempting. I'm hitting 67-70 max temp on my cores with prime95 (non avx).
I was concerned about that when installing it. I'm planning on running some tests to see if it has any impact. The idea was to directly supply the CPU cooler with air, but if it is just recycling warm air, then that won't help.