Started digging into mounting the wing. First I stripped everything off the trunk lid in preparation for painting. It was very hard getting the third brake light out, when it finally pulled free I found the foam gasket around it was badly deteriorated and was causing it to stick to the lid. Removed the license plate lights, Mazda emblem and striker. Took some acetone to remove the markings the junkyard had written on it (not sure why it had to be marked up so much, seems one spot would suffice). Then it was on to the always nerve-wracking drilling of holes in the bodywork.
First thing was to place the wing on the lid and get it in the proper position. There is a slight curve at the bottom which makes it easier to get it set in the right place fore and aft. I measured the distance side to side from the edge, that ended up being about 4 mm. I had to adjust slightly to get the same distance from the front edge of the lid (I measured to the nearest part of the bracket, that distance for me was 377 mm). Once I had that all laid out I used painter's tape to give me some reference points when I removed the assembly.
I went ahead and marked the hole for the forward fastener, it's a through hole so that was easy. Went ahead, center punched the marks and then drilled them out. I used a 3 mm for my starter hole, I didn't have any metric drill bits the right size so went to my standard drill index. In order to figure out which bit was the best match I drilled into a piece of scrap 2X4 and then tested the fit with a bolt. I ended up using 13/64" for my final size.
Next I took the brackets off the bottom of the wing:
There are two small Allen-head screws holding the bracket into the bottom of the wing. Those attached to the trunk mounts with two through-bolts. The after bolt is the one used to adjust the angle of attack of the wing:
You can see the paint on the mounts wasn't the greatest so I had to get those sprayed up.
Once I had the trunk mounts separate I made a couple of templates from them on thin cardboard. I used these to locate the other hole needed to mount them. Pretty basic so no pictures of that (hard to take a picture when you are drilling anyway). If you have done this correctly the front hole lines up with a hole on the inner stiffening frame of the trunk for access to the nut, and the rear one will be close to the outside edge. It would be a lot easier if you had the templates, but if you take your time it is possible without it.