I think the traditional hook shape was something like Shank = two times the gape plus the the eye? If so hackle shank length would raise the hook point above the water by a bit more than gape width.
In the picture SilverCreek posted above it shows the body extending ~2/3 shank length and in the one flytire posted it shows the body extending the full shank length. So in one instance the tail starts forward of the bend and the tail is longer than the body and in the other the tail starts at the bend and is ~equal to the body; so, like the real bugs not all dry flies have the same proportions. It seems after reading many descriptions of such pictures that many authors don't actually see what they describe. I doubt that the fish see what we think we see.
I don't tie or fish many conventional dry flies, but prefer the body shorter than the shank as in SC's illustration, somewhat giving an impression of a smaller bug on a given hook size.
Having observed from the comparaduns and parachutes that the fish tend to ignore the hook point hanging in the water and prefer the body in the water, I wonder if using ,hackle that is less than gape width or cutting the hackle off flush with the body on the lower side would result in more or fewer fish?
My opinion is that the traditional more heavily hackled flies are better fast water flies where the fish do not get a good look at the flies and the hackling improves floatation.
Take the the most famous caddis pattern, the elk hair caddis, as an example. It is the most popular adult caddis pattern and yet it is not even listed in the most famous fly fishing/tying book about caddis - Gary Lafountaine's book, "Caddisflies." Those of you who own a copy, check it out. Why would Gary Lafountaine leave out the most famous caddis pattern from his book on caddis?
Because of the hackled body lifts the fly body OFF the surface of the water, and adult caddis lie ON the water. So it does not present the impression of a caddis on the water. However, it is a fast water fly and a skittering caddis pattern because you can skate the fly. When I fish my old EHC's, I cut the bottom hackle off so the body is on the film.
Why did Craig Mathews eliminate the hackled body when he based his X caddis on the EHC? Because caddis bodies are not elevated above the water, they are on the water. He followed Gary Lafountaine's example.