It can be done. Increase Sky Size to 16384 and increase the terrain point spacing to 60000 with planet curvature enabled. Set the clouds' density shift to -100 and double the half heights for haze, bluesky, and redsky. Cut their densities down from 20% to 10%. If you decide to generate a terrain, go into the modify window (accessible from the terrain window) and set the height range to somewhere around -0.5 to 0.5 terrain units, otherwise your planet will turn into an oversized asteroid. However, this will eliminate any form of slope, so distribute your surface layers using fractal noise instead of altitude/slope constraints. A surface layer set to white and distributed using a large-scale fractal will have the appearance of clouds.
