Tonga; the answer is YES you can block the lower one and it helps a lot. It didn't affect the temps on mine at all. I used a thin piece of aluminum flashing cut to slide up around the edges and it holds very well. Painted it black and its not at all noticable. I went even further underneath, with the belly pan removed, theres a black plastic covering under there with an opening thats prob more than adequate for the hot air to escape, but I used a dremel to enlarge the hole further. No matter what you do that critter still emits a hugh amount of hot air, especially if you're slow riding or city riding. I also installed SpiderPops cat sheilds as well. I still don't like the idea of that motor heat going up like it does in city driving. I know the fan holds it steady after it comes on, but soon as you hit the road it cools back down. Folks here with lots of mechnical knowledge say its absolutely nothing to worry about, but no other machine I've ever owned does that.
