limited experience with skeletons but based on
this comment, i think your best bet is to create a sprite and attach it to the skeleton,
somehow.
when i attached a 100x250 sprite to the skeleton in the Spriter example via FixSpriteToSkeleton2D(), i experienced some
visual anomolies with the "collision" sprite (including a
visible CreateDummySprite() sprite that was NOT the 100x250 i set it to):
..but the sprite registered proper hits, regardless. unknown what caused the visuals... there's some scaling and offsetting going on
somewhere.
manual placement of the collision sprite based on GetSkeleton2DX/Y worked normally, of course (and i didnt try box2d methods which would allow additional sprite shapes, etc).
anyway, that's where i would start.