Skyboxes with animated clouds

Hi, I was wondering if anyone had any ideas on how to combine using a skybox for rendering far-off terrain (at the horizon) with animated clouds rendered on a sky-plane. The problem I see is that my skyboxes will have mountainous terrain and the clouds should move behind them. I figured i could just include an alpha channel in the skybox and make the sky portion transparent.. However, the skybox textures are so big to begin with that I was wondering if there was a way around it. Another way i thought was just to not have the clouds move behind the mountains in the skybox, but make a haze or fog behind the mountains that will be the same color as the clouds. Then I could render my cloud plane after the skybox with the z-buffer turned off.. the cloud plane would have to be positioned such that from the perspective of the player it blends into the haze. The other way would just be to render the far off geometry at very low detail and use the skybox just for the sky. Any suggestions, ideas, etc? Thanks, BH