Zenith Chromacolor Neck Setup

[Macdude]

I'm having some trouble setting purity using the "red blob" method as discussed in various places. My issue seems to be that I can't pull the yoke back far enough. There is a video posted to youtube that shows how the convergence cluster and blue lateral magnet is supposed to be positioned on the neck and while I'm appreciative of the video I can't seem to make out much.

Below is a photo of the neck on my set. I could be wrong, but it seems everything is a bit far forward. The convergence controls seem to work fine, both static and dynamic, I just can't set purity in the way described for earlier Zenith sets.