I'm not sure on this but I think at least 2/3 in. 20% in for sure is not enough, yes add a spacer when you find out the correct amt
start with getting a 50/50 spacing in the shroud, 75 % in, has the same effect as 75 % out, from what I've found with playing with wingcars, buy placing a sheet of typewriter paper on the grille at idle, and playing with nothing but a handful of spacers with the same car, 50/50 seemed to hold the paper to the grille, where as to far in, or out wouldn't hold the paper to the grille,....unscientific perhaps?
