I would be very surprised if any of those 'fitting maxims' developed by, and for, road racing cyclists held true for less athletic riding done on MTB or Hybrid designs. "Longer stem"? On a road racer a longer stem stretches you 'out'. On a hybrid a longer stem stretches you 'up'. Proper seat height for any bike is the one that allows the seated cyclist to pedal the bike with the heels on the pedals. Unless you have bigger, or less than, 85th percentile foot size this should get you very close to an optimum saddle height. On the road racer the next step is to fine tune reach adjustment. On a hybrid (assuming it was the correct size to begin with) you are done purchasing components. If you cannot abide by the resulting position reached by adjusting the stem height you are probably over-thinking "fit".