Bill
Unless I'm misinformed, which may be the case, I belive you will get a few extra minutes vs. the sweeps in the half.
Aren't there more than 2 corrals per wave, plus what wave are you in? With you in B, there must be at least one corral behind you, and those corrals will be filled with lots of people. The start for the half on the new course is narrow, wicked narrow, so it will take a long time for all those people to cross the start, and the 16 minute per mile clock will begin at that time. If you can get near the start of the B corral you will cross the start many minutes before the sweeper clock begins, and you'll be on your way.
If I have this wrong, I apologize, but I recall more than 2 corrals for the waves of the half marathon start.
By the way, no packets in the mailboxes in Wellesley, Massachusetts. Apparently the Disney folks or the postal service cannot find us.
Craig