Hey Kent! I'm currently making an IK for the dog's head and I'm having an issue. I scaled the head bone, I named the big one head.IK. I parented the head with the head IK, i cleared the IK's parent (alt+P) and then I wanted to fix the head in order to stay in place when I move the head.IK. Your video uses copy location constraint by selecting the head.IK then shift+select on the head. You later set the head/tail slide to 1, in order to make the constraint location on the tail. I checked your video and the head bone was perfectly places on the tail of the IK yellow bone. When I moved the slide, the bone went all crazy and was placed in the middle of the spine. Why did this happen? I also included my blend. file so you can check it out.
Here is the problem.
Hi George - After running through the setup in your file, I can confirm the issue you're experiencing but I can't figure out exactly why it's happening.
I did however create a separate chain that mirrors the setup of the neck as demonstrated in the video, and it works as expected. That means something else in your armature hierarchy is broken. I recommend trying to rebuild the rig as troubleshooting problems is often more work than rebuilding.