How is the SV-1 wired up

[McCreed]

Does the Ibanez make 2 and 4 positions effectively the same as having the middle and neck/bridge as single coils? So then only 1 and 5 give you the full humbucker, is that what you mean?

Yes, it's called "auto split". No push-pull pot required. Standard 5-way lever switch.
Position 2 gives one coil of the bridge HB and the middle SC. Position 4 gives one coil of the neck HB plus the middle SC.
The HB's coils are split so that they are RWRP to the middle SC thus still being hum-cancelling.

edit- like this:


Edited again to correct switch position numbering