Is the spoiler attached via glue and screws? There appears to be 10mm bolts (mine was missing the right side), plastics clips which do nothing and bunch of adhesive tape on each side which hold the spoiler to the trunk. I can't tell if the double sided tape is stock or not. The thread on the right side of spoiler seem to be ripped off by the previous owner somehow. In addition the bolts don't seem sufficient to hold the spoiler in place without it rocking back and forth. The clips don't seem to connect to the trunk hole either. What have you used to reattach the spoiler? Looks like the previous owner just used duct tape.
This is kind of how the spoiler on my Geo storm mounts which is somewhat partially Toyota It's a stretch I realize but still I took that spoiler from the storm and stuck it on the back of a Corolla oh god back in I don't know 92 and it mounted similarly I use the similar type of tape that you just lifted up and shown here because putting holes in the trunk would require some funky fasteners and all that that I didn't have and I didn't really want to tear up the deck lid because I knew if the spoiler didn't stay on long it wouldn't be missed It stayed on about 6 years finally fell off washing the car one day matter of fact it's still sitting over there in the corner I never threw it out I guess it's time now.
Geo prism right? Almost exactly like a corolla I wish they could have designed this better. Seems like another bolt with a gasket around the attachment points would be fine.
By the looks of it on one of my 94 5 Corolla prism Nummi cars The stiffeners that are glued / welded to the underside of the trunk lid I think we're in the way but I think on a prism there isn't any or they're slightly different shaped something I can't exactly remember but I still have the spoiler sitting out here I thought it might go on another car with all these kids but it hasn't I guess it's time to get it to the trash