Hey Aaron,
Saw a write-up in a QFM article whereby the slick rig was cut mid-way through the plastic so that the shaft of the hook is exposed - a treble was then attached (would recommend the super strong halco ones) and a large treble was attached. It looked to sit nicely and more split rings can be added if you want more movement to the treble. It looks like a strong link as the only way the treble can slip off is over the hook itself or if the split ring gives way - will be attaching a treble to slick rigs this way myself.