You're a bit behind the times, but I'm sure Pandabikes appreciate it.
Just a reminder to those considering a Xiongda. They're absolutely brilliant motors, but they do have limitations. The front one is not suitable for suspension forks with a disc brake. Rim brakes are OK and so are rigid forks with disc brakes. The back motor is also quite wide and will require a bit of jiggery pokery to get it in your frame unless you already have a wide frame. The problem is worse if you have a disc brake.
Whether front or back, you should fit a torque arm if fitting to an aluminium frame or fork.