Any time someone offers you a trade, a trade you did not initiate, they ship first.
At least in my book.
This year I've had a couple of people try to get me to ship first or on the same day and I NEVER do. Too many have been too nice in the past and gotten ripped off.
Male boas can and do get well over 6 ft. I've had 10 footers, more than a few and have personally seen a couple over 12. They are fantastic pets but do not plan on them maxing out at a comfortable size. They may. They may not.