Have you looked into Zip Charging. Your 300.00+ of chargers is = to my $20.00 setup when it comes to charging A123's. That said if you are going to use the chargers then I would go 7S.
Now back to topic. Tell us about the motors guys. Will I really be able to get away without the fan, Will I be able to tell the performance difference. What are the real world effiencies.