scene doesn't work for models. models used in a sky definition are sky entities, work rather like view entities. relative possition is in relationship to the camera origin in LEVEL X/Y/Z cooridinates
example, you set a mdl at X = 500, y= 0, z= 50;
this places the entity +500 X 0 Y and 50 Z from the camera origin
that means this entity is visible when the camera faces aprox 0/360 pan angle ( facing positive X axis).
this entity doesn't exist in the level itself, so level lighting/sun doesn't effect it. when facing it, as long as there isn't geometry or otehr entities blocking its visability it will be rendered. i.e. i place a block at +300 X quants at 100 quants tall. place my camera at 0/0/0 and turn it to face +X axis.
the mdl can't be seen. if I back teh camera up over 200 quants the entity will now become visible ( it stays always at 500 quants from teh camera)
if I side step my camera left 500 quants. the mdl is still exactly in the same spot 500 +x quants away at 0/360 pan angle
but layer for skys doesn't apply to both sprite skys and model skys, they work on thier own seperate layering. sprite skies are drawn into the infinate distant engine sky. entities are drawn in relationship to the view.
i.e. you can't layer a sky dome over a sky model
thats how a sky entity works. very similar to a view entity but its only visible in the view when facing in the direction teh entity is.