I recently had this problem with my 850T wagon. I hardly ever open the moon roof but my daughter does, When I closed it and the shade, the shade covering fell half off and was hanging down. I had just done a head gasket replacement and had some clear silicone adhesive remaining in the container. I figured that it was just going to harden so I better make good use of it. I know that the hard part is getting it under the rear trim so I made three 1 inch wide shims to hold the trim away from the closed shade so I could apply adhesive to that area of the shade. I placed the shims near each corner and one in the middle. 1 Inch gave me plenty of room to get a thin roller,like the one I used on the upper head, in that part of the shade. I emptied the container onto a board and applied it to the roller then rolled it onto the shade everywhere. Starting from the middle, I pushed the material evenly onto the bottom of the shade, pulled out the shims and stuffed the remainder under the trim with a puddy knife. It all looks real good now. I had this happen on another car but didn't fix it. I hope someone can profit from this fix !!
Ron K 94 850T & 98 V70 XC