[puddleglum]

I found on my Rondo that a full air dam hurt my mileage but a partial on both front corners and installing a belly pan helped. Different cars and different air dams are going to perform differently. You may have to do some experimenting with cheap materials first. I am a fan of belly pans. They are more work, but are more effective IMO. The other advantage of the pan is raising under hood temps and reducing warm up time in colder weather. In my mind it's a win win. Only downside I've found is mine increase cabin noise a bit.