NULL is the best choice of the 3. Also if they're showing from another section of map you could try this (although this is just a thought off the top of my head and may or may not work.)
If you have it set up like the first part, try the second section. (This is really rough, but hopefully you can understand it.)
Honestly, why would you ever use the default compiler? It's made for Quake, and it's really, really old. Use the newer ones, it solves so many problems and is tuned for HL.