As mentioned, Power'Trons aren't really suited to splitting. Despite their name, they're still a bit brighter and clearer than regular humbuckers—fairly P-90-ish, really—so when you split them all you get is a volume drop; the EQ doesn't really get much brighter, just a touch less in the low-mids but with the volume being so low it's not like you can really notice it. You've got to boost the signal back up quite a bit to really hear the shift in EQ and at that point you are of course also boosting the hum.
You get more out of a split with them than you would with regular/vintage 'trons, but that's not saying much. And though I've yet to try power'trons split in a semi-hollow body specifically, I've done enough semi-hollows to imagine the muted tone of the body would eat up any extra treble and cover for the minor loss in low-end, anyway. In other words I wouldn't expect it to sound much different from just turning the volume control down.
YMMV of course depending on exactly how you play, what you're plugging into and how your whole rig overall reacts to small changes, but, personally, I wouldn't bother ever wiring up a 'tron pickup for a split switch ever again, at least not without a custom design made specifically for it. There's just not enough meat on their bones to begin with—even the power'tron—to make splitting effective.
You could look into wiring up a bass or low-mid cut instead, which results in about the same tone but at least keep it hum-cancelling. I did that with a Cabronita's neck pickup, it was a while back now so I don't remember the cap and resistor values I used off the top of my head, but a low-cut is an easy enough thing to look up. The result, at least in that guitar, was 99% the same tone as the previous split but with no hum and a fraction more output than split, so there was no downside.
