i think we do add 9.8, heres my reasoning:
we define 1g to be normal, true weight on surface of eart, ie currently u and i are feeling 1g - ie our acceleration is (0+9.8)/9.8 = 9.8 = 1g
we feel 0g when we are in free fall, correct so we are accelerating downwrads at 9.8 to do this, ie...