Looks good Mike. I can't tell you much about the stage you are since I haven't done glass, but I would go with the coarsest disc you can put on something other than the end of your arm and knock that down in the vicinity of flat. Then don't be afraid of more bondo than you would put on a street car. This is a race car.
With the bondo at first you aren't sanding it you are shaping it, so use 36 or 40 grit on a long board and this new stuff will knock down pretty fast. I have an air long board, but haven't used it in years. I would recommend a hand one as it will go fast and you won't be taking too much off and having to keep putting more on. Don't be afraid to use a "guide coat in a can" at this step. It will let you see the highs and lows and will let you go much faster.
Once you have the shape with the coarse paper then put on a very thin skim coat on and knock the highs off with 40 grit and then sand the 40 grit scratches out with 80 grit.
Once you are satisfied with it after sanding with the 80 grit go to a high build catalyzed primer and put on 3 heavy coats. It will fill the 80 grit scratches and you can block that down (guide coat it) with 180 or 220 dry.
Finished with that put on 3 more heavy coats and block it with 400 wet. Don't sand any of these steps with your bare hands on the paper get some different rubber blocks. A hard one for the last step and there are some that are hard on one side and soft on the other for working inside curved areas. Get a long board and shorter board to use with the 40, 80 and 220 papers along with the blocks.
When sanding with the 400 paper I wrap it around a paint stick and sand, then tear off a length of it, sand some more and tear until it is all gone. Put the paper in your bucket of water with some dish washing soap before you start using. Take a sponge and keep dipping it in the water and wring the sponge above where you are sanding. Dry the area every once in a while with a squeegee and paper towels to see if you have sanded it flat. At this point you aren't shaping anymore, just getting ready for the top coats. After the 400 you can spray the sealer and top coats.
This all sounds like a lot of steps, but once you know what you are doing you could finish what you have in the pictures in a day and be ready for paint.
I like the effort you have put into getting the cage over the driver's head as low as possible. There are a number of cars that run that could sure benefit from doing that.
c ya and did you ever see if I have everything on the site like you wanted it?
Sum