[Herald1360]

Is there any realistic thermal coupling between X3 and the output devices? If not, then the bias compensation will only really be for ambient temperature rather than effective runaway control.

So far as silicon vs germanium is concerned, silicon has a higher mV change per degree than germanium (about 2mV vs 1.5mV) so if anything, using a silicon sensor will overcompensate rather than fail to compensate.

If the output stage emitter resistor goes a bit high, the effect will also be to overcompensate since its dV/dI will be higher. At least this is on the "safe" side for the output devices though it will marginally worsen the audio power output available from the radio.