A great method to help get good drag free drifts is to introduce some slack during the cast. There are many slack line casts but the Reach Mend is the most simple, if you tend to present your fly side on and at an angle to your fish - (and I suggest you do) then you’ll want to use this cast pretty much every time you throw a fly
The reason they work so well is because of the way a trout’s brain works. These fly designs are based on the most important ‘triggers’ to a trout’s feeding response – a fly’s size, shape and posture in the water. In fact, Wyatt regards a suggestive impression of a trout’s food to be far more effective than a close copy imitation. Presentation is the key. Well proven for fly fishing in New Zealand, with these flies you can confidently fish for trout, anywhere they swim.
It's important to know that overlining or underlining a fly rod will not change it’s intrinsic properties. It will, all things being equal, make it bend more or less for a given amount of line out the tip top. Here's the lowdown...
Bill Gammels 5 Essentials of Good Fly Casting. I have always maintained that if you want to improve your fly fishing the place to focus your effort is on improving your fly casting and presentation skills