Congratulations on getting your set running!
It must feel good to have accomplished that.
The ghosting and black band could be horizontal phasing as old_tv_nut suggests. It's difficult to say. A photo would really help. In either case I don't think extending the dag will help.
If you remove the 6AL5 horizontal discriminator tube the horizontal should just roll slowly if the horizontal hold is properly adjusted. Then lock in within 15-30 seconds after replacing it.
If you had a dot/bar generator or alignment pattern DVD disc it would make it easier to see what's going on with regards to the centering.
If I haven't scanned the service notes for the horizontal section of this set, or if the Sams doesn't describe it, let me know and I'll try to get them to you later in the week or early next week.
John