[aerohead]

Your image was taken too close to the car, altering what Honda's design would reflect from a telecamera or blueprint.
What California98Civic presented looks much more accurate for your purposes.
A number of aspirated,rooftop foils (as depicted on the Dodge Conquest) have made it into production vehicles.They don't accomplish anything.And as mentioned,would not effect a change unless sealed airtight against the body.
Even if the Crosstour is incorrect in profile,I don't believe you'd see any appreciable improvement unless you actually extended the length of the car.The experts claim that this is the only true path to lower drag.Of course,you could investigate the cooling system drag,underbody,diffuser,and wheel openings,idealizing everything Honda has already optimized,but beyond that,any meaningful drag reduction would only come from lengthening / boat-tailing.