My frontal area is 6-7' even things as little as this can be debated where and how it gets measured. I have to guess what my cd is as I have never had any cfd or wind tunnel testing done. I am probably the lowest budget car to ever hit 400. My personal opinion is that people sweat the drag stuff a little too much. Of course do the best job you can, but I can tell you from personal experience, that when you talk about being the fastest wheel driven car, accelerating the weight is a much bigger penalty. The people who say that ballast isn't as big of penalty as drag are wrong. It maybe true for a car that hits terminal velocity before going through the lights though.
One thing I do is compile a lot of real world data on acceleration. A 500 lb weight loss would make a bigger difference than a 30 percent drag reduction. Think about that. I dont think I could lose 30 percent in drag no matter how much money I spent.
Thanks for sharing that Eddie. I'm measuring FA as a cross section of the exposed body and appendages from nose to tail. I haven't included the wheels as I expect the nose skirt will largely cover those. Its pretty easy to do with the drawings as I can make multiple section cuts and then blend those to show the overall outline of exposed FA. The program calculates the area within the outline in whatever increments I choose.
Comparing your average 6.5' to this car at a rounded 4' shows a 38.5% reduction in FA and an identical number in body drag force shown by the HP-Lakester weight needed spreadsheet I found here on the forum. That's using the same 0.09 Cd number and 4000 total weight just for comparison purposed. I'm using 0.09 Cd for analysis because that's the published number for the Buckeye Bullet III car arrived at through wind tunnel and CFD analysis. Your body geometry and theirs appears to be very similar with yours probably slightly better because its somewhat shorter. I think the Simspeed car is probably better still because it just looks slicker...if looks alone is any way of judging such a thing. I certainly don't think it's worse.
The horsepower calculated for a given speed in this spreadsheet is bogus in my opinion as it shows you'd only need 410 hp to go 400 mph, and 1071 hp for 600 mph. Where mine are 316 hp (23% less) and 755 (29.5% less) respectively. I doubt anyone would agree with those numbers.
The hp calculator I found at
https://www.rbracing-rsr.com/aerohpcalc.html shows 688 hp @ 400 mph for you and 577 hp (16% less) for me; with 2,494 hp @ 600 mph for you and 2117 hp (15% less) for me. Given that aero drag is said to increase as the cube of speed, the 38.5% difference in FA between your car and my design would indicate a much greater difference in hp needed for these speeds all else being equal.
JL222 commented he calculated the Summer bros needed 2400 hp to go 425 mph based on available input data using a program that he owned. Unfortunately, he hasn't responded back what was needed for the Simspeed design based on the input data I posted for him. For $79 I guess I should just buy that program to see for myself. Thanks for contributing Eddie...great help!