F and H because I use my index and ring finger and my hand is large so it is comfortable to spread the keys out. It also lines up my palm so it actually rests on the palm rest. Sometimes I get too enthusiastic, so the little dash on the F key makes it so I never start mashing G on accident.
This is the sort of thing you'll have to calibrate for yourself, but do calibrate at all to find out.
This is the sort of thing you'll have to calibrate for yourself, but do calibrate at all to find out.