Bc2000 (for the BCF2000 & BCR2000)

OK, I think I might have answered my own question.

BC Manager > View > B-Controls > View > Presets (or click 'P' icon) > View > Layout or Encoders.  Double-click on one of the Encoders to open dialog (eg BCR2000: Preset0: Encoder1), click Custom Output tab, then SYX button > Insert Sysex Parameter dialog.  The Models (INI files) appear in a drop-down list.  Select the model, then, from the next drop-down list, the parameter you want to load into the Encoder/button at that location.  Eg AN200 > AEG Attack.

So, if I understand it correctly, the INI files do not define a layout for an instrument, but are just a list of instrument parameters which can be arranged to create a preset.

Still not sure how you would save an INI file.  Are they just created with a text editor, or is there a way to output them from BC Manager?