I have used 10k & 100nF capacitor.
Going up to 10 bits make it sensible, but not more. Then you have to use a separate reference voltage, and make also comparator offset voltage and nonlinearity compensation.

I'm using it in 8 bit mode. Analog voltage range from 0 .. 3.5V, cpu clock 12MHz so the measure timing is from 2 -- 1000 useconds, then devided by 4 and used as a table index for linearisation.

Franc