I just tried my latching petal with harmony/double setting on my pa1000 and it works perfectly.
MEL
Mel,
Hip Hip HURRAY 
that is what I was hoping for with my forth coming FS-5L (latching) and is probably the solution to this problem,...KORG should have stipulated this in their manual!!
So to recap I'll use a
FS-5L for VH & a FS-5U for sustain coupled together.
Thanx again MEL