Most of the times, I use my KB as a synth for acoustic bass. Bossa2 covers a nice tempo range and the bass track is not overwhelming.

Every once in a while, I'll use RTs. For Bossa songs, I use the (A:Simple) of Bass, Acoustic, Bossa 085 or 140. The 110, unfortunately does not have a simple. Tempo swapping works nicely for the range of my songs.

R