I never used dark radiant before and am currently just trying to get used to it's features. I took a skybox from this site: http://www.custommapmakers.org/skyboxes.php, named and placed the files properly according to the wiki(http://wiki.thedarkmod.com/index.php?title=Skybox_Tutorial) except I also copied the forward facing texture, put it in textures/skies/custom an renamed it to "nightsky.tga"(this was mention on this thread: https://web.archive.org/web/20091206232215/http://www.doom3world.org:80/phpbb2/viewtopic.php?t=3571). I can find the the texture in darkradiant but when I create a skybox with it the info_portalsky always ends up leaking.