The type of capacitor to be recommended for matching loops is the Philips 386
polypropylene series. Readily available in Europe in 10/22/47 values from 1nF
100nF and above in 1kV and 2kV ratings. These are high pulse capacitors
used in TV line output stages, they are also the best types to use for low pass
filters in LF transmitters and anywhere else where high currents are involved.
Silver mica types can be used for the fine tuning, as they will only take a
of the current of the parallel main capacitors.
Information has been on my web site for about three years...
73s Dave G3YMC