Panning is a pain in ARP2600 V!
I don't have the VST in front of me, but I think I did it like this:
* Take your LFO and patch it to 1 and 3 Voltage Processor jacks
* Invert the signal coming from jack 3
* Take the separate outs from Volts Processors ( 1&2 and 3&4 ) and have those control the amount of Left and Right audio volume.
You can tweak as needed to get the panning wider or more narrow, etc. It works really well when you get used to it. It would be easier to just patch LFO to the PAN jack, but that only causes a weird click to happen for me.
Hope this helps!