i hate to sound like a dummy, but i don't get the math. if you're left w/8g carbs, why not subtract the fibre? i don't understand what you're doing.
by the way, corinne netzer's figures are really different. for the same brand she's got per 1/2c: 90 cal, 9g protein, 9g carb, 1.5g fat, 5g fibre. how do we know what to believe? i've been taking corinne netzer's book as gospel!