It seems to me that hiding "non parented" entities is faster, even if you have to hide a lot of them... I use it a lot as well for my multiple renderpasses but I am satisified with a constant 25 fps ...
EDIT > Sorry I wasn't aware that you are using animated meshes (with child/parents...). So what about moving the mesh outside of your skybox and then putting it back to original position? Using Positionmesh mymesh,x,0,0 and Positionmesh mymesh,-x,0,0 ?
EDIT > Sorry I wasn't aware that you are using animated meshes (with child/parents...). So what about moving the mesh outside of your skybox and then putting it back to original position? Using Positionmesh mymesh,x,0,0 and Positionmesh mymesh,-x,0,0 ?