If I'm reading right, your "teaser rate" is the same as your current index + margin rate? If this is the case, then I would expect Laser Pro to produce the TIL with the payment streams you describe (I'm not a LP expert but I don't think it would disclose 60 payments at $XXX and then another 299 payments at $XXX as a separate stream and 1 payment at $YYY). Since the TIL for an ARM assumes the rate will adjust to your current fully indexed rate after the initial rate period ends, there is essentially no rate change in your TIL scenario.
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I've just writed a wrong.