dlm roof size

[lmdriver72]

We're having an argument in our shop about the length of a dirt late model roof. There's a grey rule at our track about the length. I say shorter is better to let the air over down to the spoiler. others say longer to add downforce. Expert opinions?

[JustAddDirt]

not an expert but.
air from roof will never hit spoiler.
especially with the nose down attitude of the late models now a days, roof is at same attitude as car, RF of roof lower than rest of roof, producing down force.