Last summer I water tested a 2005 Svfara SV696... its basically a copy of the Malibu 23xti w/ illusion tower.
It is a direct drive and had a bunch of switches on the motor box... I was expecting them to be ballast control so the spotter could operate ballast to even out the wake, etc. But they ended up being for something else.
So an answer to your question?
On a direct drive... why not put them on the motor box; however, if you pull without a spotter... that would be a bad place to put them.
I would just leave them up at the drivers seat myself.