You are tying your flies too fat!
As the euro-nymphing revolution sweeps across the landscape, a revolution in tactical fly design is taking a free ride. There will be some tying adjustment for fly tyers who are accustomed to attaching split shot to their tippets to get the fly into the zone. Without split shot dragging your offerings into the abyss, you will need to re-think your fly tying designs.
I started my journey into the European nymphing scene back when I discovered Oliver Edwards Fly Tyers Masterclass and the Czech Nymph trend of the mid-1990s. Back then, we didn’t have the tungsten beads and new hook designs. Creativity was required to tie a fly that you could fish without weight attached to the tippet. Oliver used the leaded foil from wine bottles to build the weighted underbody on his nymphs. Czech nymphs do not require much weight to sink the fly if they were thinly dressed without bulk. If you do need weight, you can add a thin layer with flat lead-free wire at the tying vice.
Fly patterns designed for optimal sink rate and swimming action lack buoyant materials and require various tungsten or brass beads for weight.
The Czech nymph has fallen to the wayside in favor of all the sexy new jig patterns we are tying. However, it was my experience tying and fishing Czech nymphs for so long that made me keenly aware that a well tied, thinly dressed fly pattern will outperform everything else in your box.
Overdressed flies will not sink as rapidly as a thinly dressed fly and tend to clumsily roll around in the current at less than optimal buoyancy. I am sure your overdressed Frenchie will catch many fish, as will your mop fly; however, you may never realize how many more fish you could catch simply by using much less material on your fly patterns. Let the weight of the bead and hooks do their job, to sink the fly. Let the dressing come along for the ride without slowing things down. Too much material on your fly can inhibit sink rate and action.
The next time you sit down to tie a fly, practice tying with the least amount of thread wraps and materials. You may be surprised by how little dubbing and other materials you need.