Is it at all possible to change the resistor value on a vertical size pot either higher or lower value to get alittle more size top and bottom, to open it up alittle more. There is a 100k and .01 cap on the wiper not sure if any of these can increase the size.

This kind of problem is going to be either low voltage to the oscillator or output stages, or low signal amplitude at the output tube grid. Or less commonly a failed yoke or output transformer. Changing part values most likely won't give you the results you want.

It’s actually a pilot 37 tv electrostatic crt , I have a small crt for it but need very little more vertical size figuring a resistor change may do it.

There's probably no harm in trying. If you look at the pot it should be easy to tell it it's set for min or max resistance.