I'm not sure what you mean by truncated? Are these midi drums or RealDrums? What combination of options did you try? And how are you creating the .wav file?

There have been some issues with BIAB and rendering to a WAV file. A workaround for this is to use the R Audio (Record Audio) button. This will create a WAV in realtime for your song. Basically, what you hear is what you'll get. You may have to work with you recording levels but it is pretty easy.

Another option would be to export the song into RealBand and work with it there.

Rachael