Last couple of years I have read authors claiming that if you wrap lead on a nymph or wet fly in the conventional manner, the nymph will flip upside down in the water. Thus, your elaborate flashback or dorsal shading or emerger bud wings etc will be unnaturally upside down. Yes, there are knots that may keep your fly right side up but I would imagine if the weighting story is true, lighter tippets might allow torquing anyway.
I dont know if these writer's contentions are true since the standard weighting and tying of nymphs work. But if true, perhaps they would work better even if the were "right side up" in the water. I generally but not always tie my nymphs in the round.
Has anyone tested conventionally wrapped, weighted nymphs and or beadheads to verify whether the nymph turns upside down?