Well the harness in that picture was unfinished and eventually scrapped because it couldn't support the weight of the wing.
I made a second harness, but unfortunately I only have one picture after it was finished but the wing is mostly in the way. Though it seemed to support the wing just fine it hasn't been tested walking around for a long period of time at a Con.
But basically what I did was I took a heavy duty backpack and cut off the front of it so it was just the backing and the staps. I sewed metal brackets to the back of the backpack using high quiality fishing line built to withstand the weight of a 30lb fish and hot glue. at the bottom corner of the backpack, I sewed on a coat hook to "catch" the PVC pipe that composes the frame of the wing. Extra stabilization, I placed a larger PVC pipe in the brackets and then slide the wing pole into the larger PVC pipe. At the very bottom of the back pack,I sewed on two work belts with a snapping interlock buckle kinda like what you would have on a fanny pack. Between that and the shoulder straps it distributes the weight between both the shoulders and back and hips so no one limb is supporting everything by itself.
When I get back from SakuraCOn if the harness is successful I'll post some pictures.
Well with the real Sephiroth it would be physically apart of him and it would have it's own muscles to hold itself up.
For my cosplay wing since it is not a body part I have to rely on a harness to keep it in place so it does not tip over. when the weight is spread out properly with a good harness it's not that bad. ^_^