It also depends on how you want the neck selection to work, and if the supplied switches are just the standard 3-way toggles or something special specific to this kit. Do you want the neck swithcing to be bass/off/guitar or bass/both/guitar (to allow you to drone one neck while playing the other)? The PBG diagram with stock switches would mean both necks are on in the middle position.
There are options that would allow you wire it with only two switches, but it depends on how you want the controls to work and how you want the neck switching to function etc. Decide on what you want to try to do and we can maybe work out a wa to do it.