[lunarhighway]

i'd try to coppy what you see on oem car... these things are a result of windtunnel and on road testing and are a compromise between good aero and ground clearance, and impact resistance. they're not prefect but if your car doesn't have them they're gonna give you a little improvement. get down and measure some cars that have them as eyeballing the scale can sometimes be deceptive. going to low can hurt aero but also you quicky lean that even with carefull parking and driving, ramps and bu

you can also go for compound dams where you extend the airdam slightly in front the the tires and place even larger dams directly in front of the tires

you can use coroplast and as long as it doesn't folds along the ribs it's quite strong, alternatively i've used cheap flexible cutting mats from ikea they're just sturdy enough and because i screwed them to the curved plastic inner wheel well liner the cure adds extra rigidity