In the following image, you can see that the I2C PWM card is mounted externally on the Pi case due to a lack of holes in the case to allow for the servo leads:
Note the following assembly details in the preceding image:
We used the Poweradd Pilot 2GS USB Powerbank to power the system which gave a ridiculously long runtime of about 12 hours for the Raspberry Pi alone, but increased the weight considerably.
The servo power is from a 4 x AA size battery holder mounted onto the frame.
The camera is mounted through a hole in the tray with two foam washers allowing easy extraction from the robot.
The shutdown and start/pause switches and LED are wired into a small breadboard area on the I2C board.