Topband: shunt feeding cap values

[N2TK, Tony]

I am shunt feeding my tower. I use a series vac variable set for 290pf. The
cap to ground is set at 380pf. This gives me a resonance at 1.840. At 1.8
and 1.9 the swr is 3:1.
What I would like to do is be able to switch a cap in parallel to the cap to
ground. The thought is to cover most of the band. If I set the cap to ground
to 335pf the antenna resonates at 1.9MHZ.
So the plan is to set the cap to ground to 335pf. Then use a relay to add a
55pf in parallel to give me 390pf. I would use the normally closed position
on the relay to add the cap so the default position is for 1.84 or
thereabouts.
Here are my questions:
I have some HEC HT50 caps. They are about ¾” diameter by ¾” long. I have a
55pf rated at 5KVDC and a 50pf rated at 7.5KVDC. Will these caps handle the
voltage and current for 1.5KW?
Also I plan on using a vacuum relay. I have a choice of an RF1E, RJ1A and a
RJ2B? Will any of these work for this application?

Tnx for the input. Snow is almost melted enough to do tower work.
N2TK, Tony