the story:
During our c5 medium/high/ Very high Downforce package development we thought a good idea would be to settle the age-old debate on the FRC Vs Base roofs. so we fired up the computer. got out our pointy pens and came up with this. 
All numbers provided are of 100% stock cars, the only change is the roof. Yes, the pictures show our aero packages but those are not finished and we didn't want to share the numbers on those until it was done
Thanks for posting the data! I've been wondering about this for years. All you ever hear is, "the FRC has more drag". This tells the rest of the story...
Could you explain what the "Balance F" number means?
20% less lift sounds like a big deal until you see how small the numbers are. I'm surprised that the OE engineering team felt that was worth the drag trade-off.
In reply to nderwater :
I think it has more to do with that balance f metric.
I think that number is a representation of the center of lift, or basically how much weight is being lifted from the front vs rear wheels.
I'd imagine the balance of lift to be much more important than the total lift value. Looks like the fast back lifts much more at the rear than the frc, and rear lift means instability at 140mph. Which is not cool.
I think I'm following -- so on the FRC it's easier to correct the F-R aero balance with the addition of a rear wing?
In reply to nderwater :
correct. when we started adding downforce the % of change shrunk dramatically. from 1 lbs to 2 lbs = 100% change but at the end of the day it's only 1lb
and to finish the comment on the packages it was a 6% change in drag between the roofs when we added our very high downforce package. it added over 990lbs of downforce at 150mph.
In reply to nderwater :
you really want your aero load to be about 5-10% rear of the chassis weight.
Corvette kits just became a little less expensive. Trunk mounts are here https://9livesracing.com/products/the-big-wang-for-c5-c6-corvette-trunk-mount?variant=32950585196621
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