Getting away from the issue of 2-3 grains of weight, and leaving spring creeks behind in favor of freestone streams and rivers, my preference is definitely for low riding flies. Foam is an ingredient in several of the flies I use - the FEB salmonfly, golden stone, and hopper patterns - but only the minimum is used, along with a deer hair wing, to keep the fly afloat, barely.
Typically, these flies are about 80% plus submerged, with only the top of the foam bullethead and the deer hair wing above water and visible. The rest of the fly - whichever pattern is considered - the FEB, the tails, the legs, the antenna, and a good part of the forward ( foam ) body is completely underwater.
Two other large flies that get a lot of play on my home water, an FEB skwala and an FEB October Caddis, are also designed to ride very low. These flies use a deer hair forward body with a bullethead since the size of the naturals doesn’t lend to use of foam. But the same 80% plus of the fly is submerged, with typically only the deer hair wing clearly above the surface and visible - again, the FEB, the tails, legs are submerged.
These flies are all also designed to have a LOT of action below the surface. All kinds of flexible things moving around down there to get the fishies attention. And a lot of the time, the take doesn’t even disturb the surface as the fishies ( mostly cutthroat trout ) just inhale the fly.
These five flies also get few refusals, and my sense is that most often the refusals are a result of a drag which puts the fish off, not the design of the fly.
So I don’t agree with the thought that fully sinking a hopper, or other large fly, is necessarily a good thing, but I do believe that mostly submerged flies that have a lot of built in action have a big advantage over all foam or other high riding designs where the main attraction to the fishy is more size and silhouette without so much, if any, pronounced action.
John
P.S. Scott - if you do come on out to Idaho for the Fish-In, I’ll give you a handful of flies and show you a couple places you can get into some nice West Slope cutts.