Thanks, the result of the effort
Thanks to all who responded, I read and considered every response. I changed the design a little and decided the slot not only needed to be 1-1/8" deep, but one end needed to be a repeatable 45 degrees. After a couple of failed attempts, a sled was made to hold a Rotozip tool. It was constructed such that it could incrementally and easily let the depth of cut be adjusted. The sled itself sits and slides in a jig that attaches to the edge of the 3/4 inch plywood. A couple of pictures are attached. There are probably better approaches, and there are certainly better designs. Using this tool set up was easy, but tedious. The 2" x 1/8" spiral cut bit tended to flex sufficiently as to ruin the first practice slot. Success and repeat ability was obtained by starting with a very shallow cut, and by sliding the tool backwards (in the direction of the 135 degree angle).
So, did it work? - we'll, the slot was perfect, but the aluminum piece deflected slightly. under a load. Ultimately a different, more conventional design was chosen. But, I learned a lot from the effort, and really enjoyed the work. My new favorite router is a small 1-1/2 hp trim router. It is very easy to use, and quick to set up and adjust.