NASCAR Racing: roof flaps, roof flaps, busch cars

Question
when were roof flaps manditory on ALL busch cars. was there a time in the early 2000 years that they were not manditory on short track cars ?

Answer
Hi Tim,

As you probably already know, roof flaps stop the car from going airborn if the air gets packed up under the car when it gets turned around.  It really comes into effect at Daytona and talladega where the draft packs come into play.  But since bristol and martinsville are low speed tracks, it would make sense they are not required, but i think they are.  Something odd may happen.
Hope i helped (sorry for the delay)
Coy Jordan