After having charged the batteries for both my hexrotor and transmitter I went out to fly and discovered several things:
1. The default PID settings worked well although there was considerable wobble (addressed below). Here’s a screenshot of the settings in the MultiWii Config menu:
2. The wobble was caused by the severe vibration of one of the six motors. The sensors on the board (accelerometer and gyroscope) were getting false movement signals as a result of the vibration, thus throwing off the stability. I managed to abate the vibration by balancing the bad motor with a zip tie (the ratcheting portion of the zip tie is heavier than the rest so it can be used as a weight is on a wheel).
3. The CRIUS SE controller board has a short on one of its power rails. Each ESC (electronic speed controller see First parts) has three wires that go to the controller board: Positive, ground and signal (marked +, G and S respectively) (see picture). The ESC has a circuit called a BEC (Battery Eliminator Circuit) that would, in a conventional circumstance power the receiver (at 6 volts). However, multirotor aircraft have a middle-man so to speak. Instead of the speed controllers getting a signal directly from a receiver, a controller board gets signals from a receiver, processes the commands from the receiver and the data from the sensors, then decides what commands to send to the speed controllers. The power distribution runs in the opposite order. The BEC in the ESC supplies a steady 6 volts (versus the full power of the battery) to the controller board (in my case the CRIUS SE), which in turn distributes the power to the receiver. This is not an issue when using in a hex configuration (six motors) because there is power being supplied from the the speed controllers for motors 5 and 6 to the good rail, but when in a quad configuration (four motors) there are no longer ESC wires attached to motor 5 and 6 pins. However, and this is strange, despite the board being unable to accept power from the shorted rails, it is able to supply power to the receiver via the rails. This may be due to the receiver pins (marked THR, ROLL, PITCH, YAW and MODE) having a power circuit separate from that of the motor pins. If in the future I wish to change the motor configuration to quad, I will have to figure out some way to supply power to the good power rials (most likely by attaching an extra ESC with no motor to work as a power supply). Here is the pinout of the board with the rails in question labeled: