Bo, I have had good luck guessing aero drag HP comparisons with:
Air drag:
Da = (density in slugs) * V^2(feet per second squared) * frontal area(in square feet) * cd (estimated) / 2
Bonneville at about 4100' is .002109 slugs, while sea level standard air is .002307 slugs. These numbers are at standard temp, by the way.
You can calculate your drag components pretty well if you know speed you ran, and your available horsepower.
Dr or rolling drag:
I had some numbers to plug in, from a Street Roadster, where I knew wheel horsepower, frontal area, tested cd, and speeds in the miles. From there, I found about 100lb rolling drag worked within the formula (for that car at that speed.). I dont have permission to identify the car and its exact numbers, but its all just comparison. Aero drag gets a lot bigger than the roll.
Also, for perspective....during pre SpeedWeek testing of the 2004 Bonneville Prius project, I made top speed push runs with a stock 245 hp Tundra pushing the Prius with no throttle application by the Prius driver. That Tundra could run about 108 by itself, and would hold 93 pushing the Prius. Most of that speed loss had to be the rolling drag and with the motor-generator making additional drag in very light regeneration.
Rolling drag changes in relation to how good the aero is, unfortunately, because the rear wheel loads up if your bike aero is poor and too high. That makes it hard to figure at speed.
HP = (Da + Dr 'which is rolling drag') * Velocity in ft per second/550.
Bottom line is that good aero is cheaper than more horsepower. You've seen pics of my bike. It is about 75 HP to the ground, and my best speed this year was 163.829 3rd mile.
My bike is about 22" wide due to wide engine and carbs hanging sideways. All food for thought and some comparative calculations you can ruminate over!
Hope this will be some fun figuring! Best of luck, and give me a call some time.
JimL