These are my atlatl throwers, they aren't very pretty, but they do work which for me is most important. I don't have any darts right now as I destroyed and lost all of them.
The shortest one is 40cm, the medium one is 55cm and the long one is 90cm(without handles)
The long one gets me pretty good ranges of over 80m(with nice and straight darts I assume it could be even over 100m) and the other two are great for accuracy(giving me range of only like 50-60m)
The long thrower is combined with a short sling so it is also a short staff sling making it still useful when I run out of darts, just pick up a rock!