Hi, does anyone know whats the best length sling for distance? I mean is there a point where youv'e reached optimal length and you are not going to get any further by using a longer sling.

70 cm for a lanyard because it's the best length for the length of my arm.
So, I reach 80/100 meters with an underarm throwing.
But I'm not looking for distance.

Im getting a 160g smooth beach stone about 110 metres with a 27inch balearic sling. A 100g stone about 170 metres with a 46 inch paracord sling. I then lengthened the paracord sling to 53 inches but couldnt throw any further. Im using a kind of helicopter/sidearm for all the throws.

How long is a piece of string? :D
It can be very variable and personal to each person. It depends on a lot of factors: height, arm length, slinging style and probably more that we aren't even aware of. I would say experiment with different lengths. It's what I always say but I think it's the best way of finding what works for you.

~90cm
I know that 1.2m doesnt feel as good as 90cm for me, don't know how it is in between

Edit:
with very thin cords it might be comfortable to get even longer than 90cm , havent experimented for a while.

Kick wrote on Oct 12^th, 2020 at 11:14am:

How long is a piece of string? :D It can be very variable and personal to each person. It depends on a lot of factors: height, arm length, slinging style and probably more that we aren't even aware of. I would say experiment with different lengths. It's what I always say but I think it's the best way of finding what works for you.

And the weight of the object being slung.

Also true.

   When I first started slinging I experimented with some crazy long slings.  Initially I did get more distance with them.  As my technique improved such long slings were unnecessary.  I found that my optimum sling length for distance or anything else is half my height.  Many but not all agree with this. 

Traditionally people will argue longer = better, up to the point where mass and air resistance of the cord become too much (this length can be increased by using thinner/lighter cords). This does seem to be backed up in the records.

Personally I throw most powerfully with the figure 8 technique which cannot be done with excessively long slings. My maximal distances are achieved with a 37'' paracord sling which is close to the limit for traditional techniques and my build (6ft tall).

It's definitely on a curve. My longest sling is I think still my one Tibetan sling which is ~126cm (it used to be 124cm but I just measured it now and it seems it's stretched) from retention loop to the centre of the pouch. It is NOT good for distance. It's very fun to use and it's not like it can't get any distance, but it just can't get the same distances as much shorter slings.