OHHHH i see what they are doing. That back piece looks like its coming up which really confused me but when I tilted my head I can see its flat, thanks!
It would be your second picture of D. If you look at on the ride side (structure thats coming out) you can see that at first you have a little knob coming out and then as you go deeper it appears to be coming out more. Its hard to proximate how long that line really should be but none of the other answers make sense