Stagger this is the post by Pcray where I adopted the term, as far as I know it just refers to a very very small amount of drag.
Im not entirely sure about the fly being upside down, ive never really paid attention, eyes are not that good, lol
Pcray:Rarely is it "seeing" the tippet. I think you could have a rope on there, and if it weren't for drag, they'd still hit. Glue a few inches of some 1x to a real bug, toss it out there, and I bet it gets taken.
Could be the wrong size, that's easy to change. Could be the wrong part of the water column, maybe your natural is floating on top and the naturals are in the film, or vice versa?
Most likely, micro-drag. A little drag doesn't necessarily spook the fish, it just makes it look different than what they're eating, which is drag free.
Finer tippets can help with drag, though I never go below 7x. Lengthening the tippet, or using more supple material has the same effect. Play with the leader and tippet length, play with slack line casts. And part of it is accuracy. With such small bugs they focus on the smallest little current seams, and you gotta be in that seam with the fly doing exactly as the naturals. Invisible naturals make this task harder, about all you can do is guess what naturals are doing by bubbles and such.