Re: Vertical casting vs non-vertical
If I understand what you mean by a backcast off to the side (rather than a slight rod tilt) followed by an overhead cast, that is an oval or elliptical cast. It is also called a constant tension cast or Belgian "wind" cast.
It is a cast that is often use when the wind is coming from the side of your casting arm and blowing strongly into your body. The side arm backcast keeps the fly from hitting your body and the overhead cast takes the fly over your head.
The disadvantage is that each back and forward motion introduces a half twist into the fly line and leader that you will need to untwist every so often.
By casting in an oval/ellipse, we are moving the rod tip in a circle for each casting cycle of a backward and forward cast. For a right hander this causes the fly line to twist in a counter clockwise direction. Take a look at how your fly line is twisted and I bet that you will find a counter clockwise twist for a right-hander and a clockwise twist for a left-hander.
To prove this to yourself, take a pencil in your like a rod and bring it back low to your side and then around the ellipse and forward high, then back low and forward high, over and over. Look at the circle your hand and arm are making and you will see that you are moving in a counter clockwise circle.
"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy