[Amps] New question

[Jeffrey Madore]

I'm working in a 2 meter solid state 100 Watt PA using a pair of 2SC2694's in parallel, with a Pi network output. The Pi network components are fixed except for a trimmer cap in the load position. With the correct values of chip caps installed, the output power peaks with the load trimmer plates fully un-meshed. I'd like to see this adjustment peak within range of the trimmer for obvious reasons.

So, I assume the best thing to do is lower the value of the fixed cap in parallel with the trimmer in the "load" position? 

Since transmitting chip type caps are expensive and difficult to find (most are rated 100 volts or less), is there any reason why I couldn't replace it with an appropriate value dipped silver mica cap rated for 500 volts, while keeping the leads very short.

I also have some ceramic disk capacitors of roughly the value needed, that came from RF parts.
Is there any advantage of ceramic vs. silver mica in this application?  However, I have no idea of the voltage rating on these caps. They are listed as NPO in the catalog. I probably should know what that means but I don't. 

Once upon a time I was smart, made the big bux, etc. Then, while bending over a machine, I had a 100# steel cover fall from 3 ft, hit me on the back of the head, driving my forehead into the solid steel of the machine I was bending over. I awoke a changed man. I could write a book about the things I used to know, if only I could remember what they were.

73 and thanks for any help,

Jeff - K1LE ><>