|Just returned from the NRA Convention in Huston, TX last week, but on the way home, I stopped buy Rantoul Ill, to visit the aircraft museum there. It was very nice with over 30 planes on display, only $8 to get in and they had a P-51H with the cowl panels off.
This last is important because they had a stool to stand on and let you stick your head inside the cowling. I took pics, 8 showing the >9" wide space between the forward edge of the cowl at the engine mounting beam and engine proper. That is a vertical space of about 19" by about 9" wide and as long as the engine inside. If a pair of 20 MM guns were installed in that space on each side of the engine, there would be about two feet of exterior length for the muzzles before they got near the prop disc. A total length of over 8'8"! Neat! Just to bring that point up again and tell anyone interested that they can see that for them selves, if they want to.