Well there appears to be data saying that additional venting does not lower the sill temp under a dynamic state. At least the minor addition of the forward facing wheelwell vents. I would challenge that data using the full venting I have. And also the effctiveness of the vents under static conditions. Or as you say, obvious idling at stoplights.
If I remember right, you put a bunch o big holes in the bottom of an aftermarket sill in addition to the forward and rear vents. I think that's a great design to take advantage of convection while sitting still and probably helps flow at speed too.
I think Ron was talking about just the front and rear openings which help, but not much......and certainly not like the major ventilation you have going on.