Hi bsbeck,
You must read the section on file size prediction. If you're converting from VHS, and you want the best quality on a CD, you also need to do "Inverse Telecine" on your source ( If your tapes are movies ). This is an advanced topic. Check the AviSynth section. The templates as posted, are just a basic framework. You can't expect to put 90 or 120 minutes with them with the default CQ_VBR values. Sometimes you will, sometimes you won't. If you use file size prediction, then you always will

Check the FAQ here:
http://www.kvcd.net/forum/viewtopic.php?t=68 and follow the suggested links.
-kwag