Stabilizing a TS-18

[Zenith26kc20]

Have started on my basket case 8 inch TS-18. Got the high voltage up last night and have a question. My TS-4's (both) are not the most stable during warmup. Has anyone tried to make the horizontal oscilator stage more stable?
I have done this on some other Motorola's by using 1600 volt capacitors in the vertical and horizontal stages but it doesn't seem to work with the TS-4's
Since the TS-18 is nealy identical I was curious. Reaching behind to adjust the horizontal constantly is a bit of a pain.
And this one is a BASKET case! No knobs, back and missing a good number of parts. I kept it because the CRT is perfect!