Before putting any sort of damper in there, try taking it down below 1. I found that the control is pretty impressive on my setup and although I haven't confirmed it, I don't think it is a linear relationship - i.e. I suspect that going from 1 to 2 may more than double the air allowed through the system. Based on my observations with coals leftover from a burn (pile up the few embers in front of the 'charcoal pieces' and increase air) putting the air up to 4 is very much akin to opening the ash drawer in my old VC - it blows air down that airwash pretty hard - I've seen ash and sparks fly back from the front of the pile. But I can then take it down to 1 or below and pretty much snuff the life out of the coals. Obviously YMMV.