After trying about 5 different UIs that came out around the time that SoF was released and that all work with SoF (though some have buggyness), I am at the conclusion that maybe something needs to be sent from the server for the Power Source slot to show up. None of the UIs I tried had a power source slot. Since it came out with Burried Sea (one expansion before SoF), I have to assume that it should definitely be working when SoF came out. All of the UIs I tried looked like they had an empty area of the inventory window that could be used for the power source slot, but none of them actually had it.
Here is a preview of one of the UIs I tried that shows the Power Source slot in the UI:
http://www.eqinterface.com/downloads...ew.php?id=9182
But, when I actually tried that UI, it wasn't there. That UI hasn't been updated since 10/5/2007, so I know it wasn't added after SoF came out. I know it isn't a big issue for now, but at some point, I will probably try to figure out what needs to be sent to load that slot in the UI. It is probably something in the player profile I am guessing.