When testing your map you shoud use the fast option for VIS and LIGHT, but never use the fast VIS for a final map (unless it's a large outdoor map, full vis will then not improve fps much)
In worldspawn you can set:
KEY: vis_derived
VALUE: 1
You can change blocksize (mainly if it's an outdoor map), see this thread:
http://www.alliedassault.com/phpBB2/vie ... p?t=143042
btw have you tested your map?, after some serious testing and when you think you done then it's time to send it. Make a xxxxx.pk3 and put the file and script in the subfolder maps/dm or if it's an obj, maps/obj. Open an existing usermade map (pk3 file) and look at the structure.