Richard Harrison wrote:

. . .
The capacitance of 1893 ohms at 14.2 MHz is about 0.000006 pF. If the
plate size is kept significant, the spacing should be good for 12 KV
with no problem.
. . .

By my reckoning, a capacitive reactance of 1893 ohms at 14.2 MHz is 5.9 pF.

Roy Lewallen, W7EL