All are Down Rails except III a.
To me a 'Down Rail' is where the apex is lower than 50% of the rail height.
Irrespective of the boards thickness, deck contour or tuck/edge/roll where it joins the bottom planing surface.
With the IV (Greek) one being the ultimate example of a DOWN rail.
hey tony, got rail closeup pics of your 7’ down-rail egg? this was a great, informative thread btw
cheers,