Magnat, I don't know if you read my previous post, but you should be able to do the same thing using one battery pack with the two hotter motors. The key is to use 30A automotive relays to send power to the motors while using the 7.2V from the stock ESC as the actuating signal. This will increase your current draw without actually running the extra current through the ESC and risking a meltdown. It also allows you to keep the stock vector thrust control. If you have ever done any accessory wiring in a car (airhorns, stereo amplifiers, etc) you should have no problem. If you haven't, just let me know and I'll send you a wiring diagram.