I started palm up. My opinion is palm up should be “most efficient” since naturally palm up becomes palm down when you swing your arm to the rear.   That is, from arm-at-front to arm-at-rear there is no wrist rotation required.

But after learning the Figure 8 palm up, I now use “palm towards stomach” with my thumb pointing upwards.

This forces an extra wrist turn to get to palm-facing-downward when the arm goes to the rear.  But from my baseball background I never hold a baseball with palm upwards…..so turning my wrist seems more normal (baseball-ly) and natural to me.

Aside from personal preference I don’t think my starting position adds any benefit. In fact, one could argue my starting position adds unnecessary or inefficient twisting of the sling.

You can see the sling twist and the untwist during my figure 8 windup.

bandit111964 wrote on Aug 10^th, 2026 at 10:02am:
I noticed the same thing when I tried a training exercise with a similar swing while standing with my right shoulder against a wall. When the palm is facing up, the elbow doesn't swing out as much as in other positions.
But I don't know if there's anything useful in this. I assumed that this way my movements (including my elbow) would be more uniform, and therefore the technique would be more stable.

bandit111964 wrote on Aug 10^th, 2026 at 10:02am:
Are your cords parallel when you hold the bag? It looks like in the first photo the strops are already crossing before you start slinging.

Rhodophyta wrote on Aug 10^th, 2026 at 11:57am:
Actually, that's not entirely true, since I often throw from a palms-up starting position. And here's another point. Perhaps one of these positions can impart additional spin to the projectile, which can be beneficial for lift. Perhaps the combination of the starting and finishing palm positions is important.

Rhodophyta wrote on Aug 10^th, 2026 at 11:57am:
Yes, that's true. Please ignore this, I noticed it while I was already drawing.

My first photo cords not twisted. But due to lumpy rock fitting off center in pouch one string pulled tight and other loose.  Guess that is not ideal either! 

Rhodophyta wrote on Aug 10^th, 2026 at 6:37pm:

I have a hypothesis that the projectile's trajectory itself depends more on the position of three points - the shoulder, elbow and wrist. To be more precise, it depends on the plane in which the arm opens, i.e. the direction of movement of the hand from the shoulder. Like how a trebuchet opens. After all, his trajectory is precisely vertical. But if we (right-handed people) move our wrists like we're drawing a sword from behind our back (back left - top right - down left in front), while keeping our elbow close to our torso, then the projectile's trajectory will also become diagonal (from the top right diagonally down to the left).

In turn, it is the rotation of the wrist that determines how much the elbow will be pressed to the body or turned outward. The initial position of the hand corresponds to the position of the elbow at the beginning of the swing and movement to the middle, and the position of the hand at the moment of release corresponds to the position of the elbow at the final stage of the throw. I don’t know if I’m explaining it clearly or maybe it would be better to try drawing it.

These are all my thoughts about the trajectory, but the position of the hand also, in my opinion, has a greater influence on the rotation of the projectile to the left or right around its axis (supination, pronation).

I have my palm facing down. That is the position my hand gets in when I swing it in front of me. It feels the most natural for me.

For my distance slinging style, which is just distantly related to figure 8, I use palm up, because this is the starting position which leads to a reliable rifle spin release with a 50 inch sling and the ~45 gram stones I use. I figured it out empirically. But this is a very specific case and it might not work for you if you try to copy it. Everyones throw is a bit different.