Spence, are you buttering me up? :) Are the fish safe from you or me? Do they tremble at our vibes? Sadly, no. The Gods are always throwing enough lightning bolts that fish and fishers alike run for cover, reminding us we're all merely mortal after all (sigh).
Following are some of my stabs at the benthic macro-critter "problem", so called bc FF's can't solve it by being dainty.
Jonathan, all you have to do is add weight to the shank to flip the hook upside down. Lead eyes and/or lead strips tied alongside the shank. Reserving buoyancy and drag to the now-topside of the fly helps too.
Weighting is esp important to mimic large benthic critters: crayfish, hellgrammites, sculpin, darters, and some other small stream fishes like dace. These are not components of the drift so the fishing is different -more direct. You are slicing current as much as courting it. Going up in tackle (6-7wt) helps, and with many of these flies you are still "slinging lead". You begin flirting with the edges of the question: “Why am I using fly tackle?”
Here are some larger critter flies I came up with for browns and smallies (surprisingly similar fishing), although I've also caught big 'bows, pike and carp on them too while fishing for the others. These are weighted with lead eyes and/or lead strips lashed to either side of the shank.
These images are all digitized from transparencies…
The first two are of the UltCrayfish, the fly version of the spinning jig. It is simply deadly. Trout and I appear to be speaking the same language when I tie it on:
The UltCrayfish is tied with hair (squirrel or Austalian Possum) which limits the fly size. I tie them on 3xl #10 Mustad's (9671 I think), the largest I could tie them. So for larger craws I had to look elsewhere:
I use poly felt for carapace and yarn for pincers, and I think a #3906B:
Feathers work too of course, esp in slower water, but are more fragile:
I messed around with Swiss Straw but found it too fragile, esp for toothy browns. Also in this image is a Clouser-esgue dace pattern:
This is the UltScuplin. It looks like a sculpin and acts like a sculpin. It swims. The color mismatch here was on the day I discovered the sculpins in this particular clay flour-laced stream were a pale olive. I then tied the UltSculpin in a pale olive too. I often fished this stream at the dividing line where browns petered out (but were big) and the smallies appeared:
The UltSculpin looks much better in the water than on the vice. And it doesn’t look bad in the vice: