Hey, I have one of those!
http://antiqueradio.org/zen28.htm
It's a good performer, once restored. If you haven't already done so, you should replace the electrolytic capacitors and any paper/plastic capacitors, as well as the selenium rectifiers. This article has basic info about recapping:
http://antiqueradio.org/recap.htm
Squishing at the top of the screen is a vertical linearity issue. There are adjusters for height and linearity at the back of the TV, although you may find that the problem disappears after you have recapped the set.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html