Southpaw,
It may feel awkward, but you are doing the style pretty much correctly. There's some differences in detail from other examples. I have links here to Mark Weaver's videos and to Nwmanitou's, to go with my comments.
Weaver kept a upright stance in
this video
, similar to yours. Nwmanitou also holds an upright stance in
this video
. Because of that, you all swung the sling in a non-vertical plane. That's what Curious_Aardvark was talking about. By contrast, when Weaver was
going for power
, it looks like he leaned backward so that the sling swung in a vertical plane. It is a bit difficult to be sure of this, because this video was shot from the side, not from behind him. But my own experience is that when I lean back like that, my sling swings in a vertical plane.
Weaver held his sling at waist level, at the start. Nwmanitou had one hand at waist level and the hand holding the pouch at about chin level when he started his swing. I have tried holding the sling low (similar to Weaver) and high (similar to you), it doesn't seem to make that much difference.
It looks to me like Weaver used a sling that was longer than yours. My own experience is that I am more accurate with the figure-8 if I use a longer sling. The sling I like best for figure-8, stretches from the tip of my middle finger to the middle of my chest, with my arm stretched out beside me (the sling is folded in half, with the pouch held out by my finger). I can use my shorter Apache-style sling with the figure-8, but the action is quicker and I am not as accurate.
Not all of us are saying the same thing; it just shows that each of us are different and (given the basics of a style) we each tune the movement and the sling to our own body.