Hooking up the components of the Paris MultiWiiCopter V4.0 board is a pretty straightforward job so if I can offer any advice, take your time and make sure not to miss any pins like I did. After making a concerted effort to have neat wiring and solder joints between the Arduino Pro Mini, the Wii Motion Plus, the BMA180 accelerometer and the BMP085 Pressure sensor, I found I wasn't getting any output from the sensors in the MultiWiiConf software. After deconstructing the board sensor by sensor, I found pins A4 and A5 from the Arduino board to the Paris board had been missed so effectively they weren't connected to anything. Now those particular pins are pretty important (well I guess most pins on the Arduino are pretty important to connect) as they take the input from the sensors! They're labelled as SDA and SCL and carry all the important stuff from the gyro, accel and baro sensor as input to the Arduino.
If you're familiar with the layout of an Arduino, you can see in the photo below the two pads in question missing any connecting pins. After soldering up these pins, everything worked fine.
*August 2011- Some more info on hooking up the baro sensor (http://fangin.com/blog/2011/07/26/connecting-the-bmp085-baro-to-paris-v4/)
*9th October 2011 – Added two pictures to show the connection between the BMA180 SDI Pin (#7) to the SDA connection on the Paris board.
*23rd December 2012 – Added a picture showing that I soldered the DC Bus closed. The advantage of leaving it open is to prevent noise entering the CPU and sensor section, the downside is a seperate uBEC is required to power the ESC / Servo side.
Troubleshooting the new V4 board by connecting the output of the new WMP into the old (known working board).