Well, if anybody does know the link, notify me, but in the meantime, I've found this: http://simviation.com/1/search?submit=1&keywords=oscar+cloud&x=0&y=0 It is meant to provide less gpu-intensive and more realistic-looking clouds. However, it does come with high-res clouds if you have a good graphics card.

I'm now getting 20FPS and 15FPS in metropolitan areas--all sliders are high or max with the exception of clouds. (Personally, I think those are good frame rates. Some people demand 60 FPS, but I don't notice any major difference after 15-17FPS).