[Boatanchors] PA Tank Circuit Padding Capacitors

[David Stinson]

Given: 
Series-feed Triode PA tank with link-coupled output.
350 VDC B+, about 9 W out on 75 Meters.
Padding across the tank coil with a 50 pFd doorknob 
was successful in lowering its resonant point, 
but space is severely restricted and doorknobs 
can be expensive.  
*Rewinding the coil is not an option.*

What other types and specifications of  available
capacitors would you recommend for this service?

TNX OM ES 73 DE Dave AB5S