[old_tv_nut]

Converting to a glass CRT but still using the plastic boot to hold it in place, right?

If you ground the dag and the boot, then the voltage is between the inside dag of the tube glass and the outside dag, so it's only that pair that makes a capacitor. It doesn't matter how many layers of grounded stuff you add on top of the grounded dag, since there is no voltage between those grounded layers.