I'm generating 100 watts into my 50 ohm dummy load but
only getting an efficiency of about 50%.
The output transformer toroidal core is getting quite hot and I
suspect that it's permeability is too low as the capacitance
required
to bring it to resonance is far higher than those of published
designs
in the LF Experimenter's handbook, using the same number of turns.
These capacitors are running very hot too (as mentioned by PA0SE in
his LFEH article).