X2; your symptom is a classic, called "blooming", where the excessive loading of the augmented current of brighter overall screen level draws down on the HT. If the supply can't cope with this then the voltage drops, and the accelerating force on the electrons. With less force to propel the electrons to the face the deflection coils have a greater influence, bending the beam further, causing the oversweep of both V and H. Focus will also be lost and, as the HV gets weaker, a dark spot develops at screen center, leaving only the perimeter visible. The width control loading that reduces horizontal deflection also apparently loads down on the HT in your set, causing the problem. When the setting is changed back to the original oversweep condition then HT is sufficient to cope with changes in overal brightness levels.
On the basis of your having recapped everything (except the tuner, and I would advise against going in there, as there are a mess of capacitors with critical temperature coefficient ratings, and they're probably OK) and assuming you have replaced the tubes mentioned in the previous posting, you may have to study the flyback itself more closely, sorry to say.
