First, I apologize for this “focus” effect – my camera was in a weird setting.
Side by side you see the F-4 (Mk.7H) left and F-8 (Mk.7F) right. The only difference is the inertial reel charge attaches to four holes on the left side when looking from the front.
I measured down 3 3/8″ from the top for the first row of holes…
And 7 1/2″ for the second row of holes.
Then from the left the top two holes are 2 3/4″ and 3 1/4″
And measured from the inside was 2 3/4″ and 4″ respectively.
Finally, the hole size is 1/4″