looks like artistic license.
Just totally impractical to hold your stones like that - and like david says the stance had been modified to fit the cup/coin/plate.
His starting balance is all wrong.
I suspect the artist had never actually seen a slinger in battle and just had a model (non-slinger) strike an interesting pose.
As common back then as it is today. Ever wonder why so many classical paintings with lots of figures show them all with very similiar features ?
One model used for them all.
Now I know historians like to put a lot of weight in decorative illustrations - but surely somewhere along the line you need to apply a little common sense, practical knowlege and physical reenactment ?
Just try this.
Grab a sling, and attempt to strike the pose in the picture (yes I just did).
It's doable but it puts your weight in a finishing position not a starting position, and as for the arm positions. About the only sensible thing you can do from such a pose is a simple straight arm overarm trebuchet style throw.
A bit like one slingbadger is fond of (accuracy is a bit hit and miss - fortunately he managed to miss us lol) but without any of the power as the starting position is just so awful.
So given that the pose is utter nonsense - why should any weight be placed in how the sling pouch is being precariously balanced ?
Or for that matter it's size or contents ?
This is a serious question as a tremendous amount of 'knowlege' seems to be derived form pictures like this one.
Is the lack of skills on the part of historians responsible for really screwing up a large number of historical 'facts' ?
It's like reading a Dan brown book. If you don't know anything about the technical aspects of the book - it's a cracking good read.
If - on the other hand you know something about them - the books are complete and utter nonsense. Take the book angels and demons, as just one example. If you know even a tiny amount about wireless networking you know for a fact that the antimatter could have been pinpointed to within a few yards in about 20 minutes - max.
So is a lack of weapons knowlege/experience seriously skewing the way that historians report ancient weapons usage based on decorative and unpractical illustrations ?
Discuss
(try the pose first - then vote)