Here is a photo (click to enlarge) from the install of the sonar range sensor (the Maxbotix EZ0) and, as you can see, the sensor fits beautifully!
I moved the RC Receiver and Gyro electronics back to the position they were in when I bought the helicopter, and it has massively improved the flight stability, so I will stick with the layout that the designer's chose...
I can not wait to get cracking with the code now!