if that ball shaft is made of plastic, I think you should seriously consider bying a pipe clamp and tighten that to avoid having that ball crack and your light falling on the ground, rocks or concrete!
Make sure you have the spirals all the way around, not just partial, because those will give some "gripping" to prevent the clamp from sliding off the ball. Once the clamp is tight, that will reinforce the shaft and minimize cracking from weight load stress on the weakened shaft that you put the screw into.