In addition to your calculations a jury will have to consider the following:
-IIRC, NINE residents called 911 having heard the gunshot at 7:16:41 pm which is over three minutes AFTER GZ claims he was attacked 100 feet away from where both SPD and SFD say the body was found?
-Why did GZ decide he needed to walk to the next street over for an address after 18 seconds of following TM when he parked his truck and walked right past the front of 1211 Twin Trees Lane during this 18 second walk?
-Why did GZ tell the 911 operator he didn't know an address at [3:25] into the call when he supposedly started walking to get an address at [2:26]?
And I can't wait to hear his answers, to those questions. I think his major slipup was not realizing that when he called LE dispatch the calls are recorded and timestamped and just did not think out a reasonable timeframe for him to be where he was, he just knew he could not admit to following and trying to stop Trayvon...and it's going to bite him in the Keister. IMO JMHO and stuff.