FLO was originally a
fernandes sustainer. that would have a dummy neck single coil for asthetics.
I know Vai sent an axe to sustainiac.com, but have no idea what happened there, or what he's using now. Not sure if his Ibanez contract would limit him from publically endorsing a sustainer, or posting more details. The lack of info presented leads me to believe that could be a factor, along with possible less than 100% satisfaction with whatever system is currently being used.
I can say after his NYC appearance for the NARAS that he should leave the sustainer axes home unless his
guitar tech is not at his side to change batteries and keep it purring

...glen