So you say that you didn't notice the laptop temperature getting any lower, but this isn't too surprising to me, since this thing is going to be highly thermally limited.

I suspect that your setup is doing something, but the thing it's doing is allowing your laptop to sustain a certain performance level for longer. So what I would look at is some performance metric like e.g. peakflops() in a loop, or a video game FPS counter, and compare with and without the external fans.