I did fix one set of drivers permanently to the baffle and while it did make a difference, it was quite small and certainly didn't fix the midrange peak of the SR-404. Going by my experience with the SR-007Mk2/A this shout has more to do with the distance from the drivers to the ears which is why my well worn set doesn't have any. Either that or it is an Airbow SR-SC1 with the label on the plug removed...
The baffle is aluminum and it is quite thick, 3-4mm.