Thanks Sparky. What class are you quoting? I will be running at the ECTA, never on salt for this tin can, although El Mirage is not out of the question (dirt). I am building for the Modified Sports class, which seems to be pretty well open to modifications forward of the cowl. So I was thinking that airdam mods were unrestricted. In that class bumpers may be removed and streamlining is unrestricted as I read it (ECTA rule book, not SCTA). I think for now I would like to limit this thread to aerodynamics concepts rather than rule books. However, you are the only person offering advice so for that I am thankful.