Hi Carl sorry for delay. I hauled a seat up and took some measurements.
A = 3 inches even
B = 2 15/16"
C = 4 5/8"
D = 4 5/8' (makes sense)
E = 4 inches even (It does taper)
Here's another picture of the top of the seat back for reference. This is my former drivers seat so its in a bit rougher shape than the one in the car bit good enough for measurements I think.