You still need to have the original or some adaqate as a head liner. If your car is called out by another competitor or a judge as being suspect , we can require to see any part of you system including under the headliner. We had a guy from Iowa who had his sunroof covered with wood then a pieces of material. It looked stock but wasn't of course , so he had to take it down to compete People do these mods to get louder of course. But in the lanes in certain classes it's cheating and not allowed so Steven remember if you do this and you compete in db drag you will be placed in an extreme class so you better be doing a 160+ to even contend in the bigger shows or finals this is why most street class cars don't have sunroofs