Bjorn, do you have a pic of those installed? Mine was an original AC car and had the X panels. I made a set of filler panels to go all the way around the bottom and sides of the core support. I've also filled about every hole and crack on the front with insulation, testing to see if ti made a difference, nothing yet.
Only thing that seems to have helped so far was adding in the "trapdoors" to the fan shroud.
