Hey man,
The 7xl is only good up tp 4s, so wire your 8000 packs in series, for 8000 4s. You cannot mix and match battery capacities, so leave the 5000 out. The mm is really only good for 4s, and leave the lvc on too.
Check out the 2nd post in this thread:
http://www.rc-monster.com/forum/showthread.php?t=10531 should help explain the motor deal.