Please read my post again. What I said is that vegas does not recognize avs scripts (unless grammar limits tricked me and I actually wrote the opposite without realizing, in which case I apologize).
If closely following the steps in the avtech to install avfs and pismo does not work, the next best thing I can think for frameserving is ffdshow's MakeAVIs, or perhaps VFAPI as a third alternative, but they aren't too stable, much less than avfs+pismo already is, and it isn't the best, really.
I would really suggest you to make lossless clips, but if HDD space is an issue to you (and considering that new HDDs aren't as affordable as they used to not too long ago), then trying a less stable solution and hoping everything goes well is all you have.
A further read about frameserving can be had here: http://avisynth.org/mediawiki/FAQ_frame ... _utilities
It is quite useful to understand why avs files are considered to be avi files but are not compatible with certain programs, and the reason is quite simply that uncompatible programs do not rely upon windows to do the work, but have internal splitters and decoders instead, and as such avisynth scripts cannot be used directly, since those programs do not have access to the avisynth.dll.