From your description you are using the neck (bass) pickup. You might want to have the pickup selector in the position that both the bass and treble pickups are included in the sound.
I would also make sure the 2-position Q switch is in the on position (usually down when you are playing the bass), otherwise you won't have much attack for slapping. To include higher frequency sounds, make sure your filter frequency control is rotated more toward the clockwise (the upper limit is about 6kHz).
The gain pots on the inside won't have any impact of the tone - they are just gain for each pickup. If you need more output, there is an RF upgrade available for the Distillate electronics that also includes an increase in gain.
Stainless strings are a good suggestion as others have chimed in. Strings are a great way to experiment with the tone on an Alembic bass. Even if you have a favorite string on another Alembic bass, it doesn't mean it will be the best string for this Alembic bass.