I just had a chance to catch up on what you are doing. We did some wind table testing some years back with a selection of tamiya bodies, a pair of digital scales in a platform table, and a large industrial floor fan. We found the weight of the front and rear of each car with body, without the fan on. Then turn on the fan to low about 15 mph, and recorded the weight of the car, and turned to high about 30 mph, and recorded the weight again. I see in your results you show you have downforce on the front of your body. We never actually saw this. We believe it was because of the shape under the front of the body. The fluid test may not be taking into account. We foung that a car with the least lift is actually what your looking for, in a sence, that would be the most downforce!
Kevin