This issue and inversions have been discussed quite a bit and I know of no direct solution.

The simplest solution is to create a Midi bass part on the Soloist track that does what you want, muting the RT during this.

If you have to have a RT, use RealBand and generate the RT bass until you have the note(s) you like. Then use copy/paste to move it where you want. Save the bass track to a WAV and use that audio in place of the bass part in BIAB.

R