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You’re right on the money with your suggestion. This scheme is exactly what I used in my evaluations of after-tuning-coil efficiency, both in simulation and in actual measurements with a scope.
My choice of capacitor and resistor values were only slightly different: 30 pf and 33 ohms, not significant enough to affect the efficiency results.
The dissipation factor, aka ESR, of the capacitor is an important consideration. I use a 30 pF Mica capacitor. Its DF is 0.3% resulting in an effective series resistance of 9.04 ohms at 1600 kHz (higher at lower frequencies). That’s significant when compared to the my 33 ohm ground resistor, so it must be factored into the results. By factoring the capacitor ESR into the measurement results, you get higher true efficiency.