Careful. The Transpac is really designed so that the cam bands thread through the webbing in the soft "plate" of the TransPac. Threading in this way will not work with Oxycheq wings, because the wing is so narrow. What will work is to use sex bolts to attach the TransPac, Oxycheq wing, and a single tank adaptor, and then thread the cam bands through the STA. But then the whole weight of the tank is borne by the soft plate. If it holds up, it's a great setup. But there's a risk that the bolts will tear out of the soft plate, in which case the wing and tank will separate from the diver.
Dive Rite does make "stainless steel TransPac Stabilizing Plates" (check under Hardware on the Dive Rite web site) that fit between your back and the soft plate, and provide additional support for the two mounting points. They're designed for when one uses the TransPac with doubles, but would serve the same purpose here - the sex bolts connect these "stab" plates, the TransPac soft plate, the Oxycheq wing, and the STA. I haven't tried such a setup.