I would try to estimate what the "attitude" (nose up, nose down) of the car is at trap speed. Sometimes a high res video from the lights will help, plotted against static attitude. They used to duct tape sticks with stripes painted on them to the fenders vertically - shows how far the suspension sinks.
If the car is nose high at speed a nose dam, spoiler, lip, splitter (extends forward but not down, still helps) will probably help.