This was exactly what I tried, I had the the ball shaft oriented vertically, and the upper leg socket was horizontal, I also tried a few other angles where the ball and socket are basically independent, and there is no support between them, yet, in all cases, the 2 parts were fused together.
Only when the gap reached about 1.25mm did the parts separate, but even then, the surface quality was bad, and the joint movement was very rough, so eventually I had to cut my loses and just split the piece. That worked just fine.
http://forum.formlabs.com/t/warhammer-40k-imperial-knight-paladin/10993/19