Experience is a great teacher. If I could just learn to stop blistering my fingers with a covering Iron, it would be great.

With all the small electrics these days, many have half-spans that fit nicely across a roll of covering instead of the traditional endwise layout. These also tend to have very lightly constructed wings with no sheeting. Ergo, a high chance for a sideways, dippy covering job. Also, since the wing depends on the covering film for strength or at least stiffness, a dippy covering job will sacrifice properties in that regard also. And it's already been pointed out in this thread that a dippy covering job deviates more from the intended airfoil--sacrificing flying performance.

The Covering material's direction oughta' be in the instructions, both for the covering material and for the airplane.