[justme1969]

This plus more was discussed last year, and there was another point I did not see brought up here.
The point was some times peculiarities also cause even more cd when lowering.
Depending upon vehicle design boundry layer frontal charged air may condense more acting as said, instead of going under a vehicle only slightly compressed.
Thus you end up with a nose speed brake effect even worse than your typical wind screen area.
" here is where the differance between air dam and frontal pitched spoiler count."Sorry if I muck things up by adding this point but it is relevant.