[hddherman]

I don't have any measurements other than the general observations that I shared in the post. It should work better than having it lie down on a wooden desk, for example, as that greatly limits the cooling potential. You only have a tiny gap where the air can move in.

It might be that your fan might be old and worn out. As someone who uses older laptops and has given out T420/X230 type machines to family members, I've noticed that sometimes tilting the laptop under use results in vibrations coming from the fan, likely from it being worn out and the blades touching the heatsink and/or plastic.