Suppose John's carb factor is 5 and his correction factor (insulin sensitivity) is 50 (Correction factor is high because he's honey mooning). He eats 30 carbs with a pre-meal BG of 100. With a bolus of 30/5=6 units. Suppose his 2 hour post prandial reading is 150 which is quite good as we're taught(20-50 more than pre-meal). At this point there is 1.8 units of active insulin (BOB) in his system (John Walsh: To calculate active insulin: 30% bolus 'consummed' every hour) equals: 6 x 30% = 1.8 units. So now he has 1.8 units of 'ready to hit' insulin in his system while almost all his meal carbs have already been converted to BGs and coverred by insulin. Now imagine what could a 1.8 unit excess insulin do to a person with a correction factor of 50. You guessed it: A 90 point drop in BG!! I want to argue that being in the '20-50 higher than pre-meal' range is kinda impossible without suffering from insulin excess (carb deficit). Maybe that's when dual/combo bolus comes to play. i kinda believed though that dual/combo is useless and by useless i meant logically impossible. My reason was that even though the 'curve' shown to us about dual bolus is seducingly similar to that of a real pancreas, but since even rapid acting insulin is way slower than real insulin, this 'fake similarity' shouldnt mis-lead us because a normal bolus would possibly match pancreas's secretion better than a dual one which is way slower.