Ok guys, going to update this since version 2 is now done.
I Re-designed the mounting points. At first I had drilled/tapped holes in the frame rails and bolted aluminum L brackets to them. To simplify, make a stronger mounting point, and save weight, I changed the design to a small section of angle iron welded to the frame rail with a weld nut welded to that:
Fabbing the new mounting tabs:
Old tab design, total weight 281 grams:
New tab design, total weight 157 grams:
Tab welded to the frame rail:
Version 1 of the flat bottom, post- Auto Club Speedway. It survived the day, plus hundreds of miles to/from the event on the highway, but it served its purpose as a prototype and now its time to move on to something that won't melt
Version 2, lighter and more rigid, plus almost entirely aluminum, so no melting! Total weight is down around 11.5 lbs! I re-used the rear side sections since they are nowhere near the exhaust, and that way I didn't have to re-make the NACA duct that supplies cool air to the differential:
Just finished mounting version 2, and mating it to the rear diffuser. I'll take a mounted picture tomorrow.