Let me help you save some time on trial and error with WSF (nylon):
-2mm wall thickness is the max you want for action figure walls and socket-walls whenever you can, unless you're doing long pieces.
-For ball-sockets using a ball diameters 5mm or more, make the socket inner diameter always 1mm smaller than whatever the ball diameter is.
-Use relief cuts for sockets and peg-holes. 0.5mm wide is all you need for some, but depending on the socket (be it a standalone joint or a socketed part of the figure) the relief cut may need to be wider and stretch beyond the socket or hole. Pic related.
-Peg holes for affixing a joint can be 1mm or less narrower, depending on peg thickness. 2mm pegs can get by with pegholes being 1.85mm in diameter so long as they're in the same print. Make use of relief cuts as necessary to allow some flex without getting too loose.
(next post I'll show a socket joint I use for 6mm ball-ends)