Dean,
Here is how I set the Sampletank drums to play.
1. The drums on the Drum track, need to be midi. By default, BIAB automatically substitutes Realdrums for midi drums. If you right-click on the drum track, one of the options in the pop-up menu is to force the track to midi drums. (Note: If you are using a Realstyle, there may or may not be underlying midi drums. If there is not, it will be necessary to load midi drums onto the Drum track.)
As you can see above, the name of the Drum track will be written in yellow when midi drums are present (green writing indicates Realdrums are present).
2. Enter into the VST plugins and put Sampletank on the Drum track (#1 - #4 on the image below).
3. Load one of the Sample drum kits onto Channel 10 (as shown by #5 on image above).
4. Exit the VST plugins window and generate song.
Hope this helps,
Noel