Oh, ok, so it's not for me, I've ordered the 50w standard version. It should arrive here next week. Does the half power switch simply get off two power tubes?
Take a look at the 36 watt layout on the Ceriatone site for a "similar" wiring of a half power switch. It is a fairly involved addition.
IMHO a half power switch on this particular amp is a bad idea. These amps get their overdrive from the preamp into a clean power section. With the extra 2 6L6's you are going to get a bit more headroom and a barely perceptible increase in measureable volume over the stock version. However, the quad version has a fuller, rounded out, complete kind of tone to it. That is the only difference. So, I would suggest either hard wire it for one or the other and leave half power switching for amps that get their signature tones from overdriving their power sections.