I uncovered a chin spoiler in my parts pile that I had purchased early on, but had gotten buried in other things in the garage. The spoiler is from OER, and is plastic. I also purchased struts and a fastener kit for it.
The top edge of the spoiler attaches to the lower edge of the front valence panel with several bolts. The center attachment point uses the lower hood latch support bracket bolt. That part went very smoothly. The problems started with the struts.
There are 3 struts in the kit. When I was working out the installation, I did some reading and found out there is conflicting information about the struts. The center strut was pretty straightforward. That goes from the front center of the spoiler to the front of the skid plate in the middle of the subframe. The two side struts are where the questions come in. Some things I found said that they should go to the lower front fender edge. Others said they don’t really go there, and if you hit a curb with the spoiler, that will bend and damage the fenders. Another theory was that the struts work with the stock GM spoiler, but don’t work with the reproduction ones. Yet another writeup described running them straight back and attaching them to the bumper brackets.
In the end, I decided to only install the center strut. I drilled a hole in the skid plate for the bolt, and left the outside struts off. It’s solidly mounted, and seems ‘good enough’ for now.