As i am starting to document this build whilst i am already halfway through, here are (nearly) all my usefull references up-front, in the hopes that it may provide more use than lots of links dotted around the various sections.

https://github.com/FastLED/FastLED/wiki/Pixel-reference
https://www.arduino.cc/en/Main/ArduinoBoardProMini
https://www.arduino.cc/en/Guide/Troubleshooting#upload
https://github.com/FastLED/FastLED/wiki/Pixel-reference
http://forum.arduino.cc/index.php?topic=140494.0
http://bildr.org/2011/04/sensing-orientation-with-the-adxl335-arduino/
http://42bots.com/tutorials/arduino-script-for-mpu-6050-auto-calibration/
https://www.i2cdevlib.com/devices/mpu6050#source
https://www.i2cdevlib.com/docs/html/class_m_p_u6050.html
http://www.geekmomprojects.com/gyroscopes-and-accelerometers-on-a-chip/
http://engineering.stackexchange.com/questions/3348/calculating-pitch-yaw-and-roll-from-mag-acc-and-gyro-data
http://www.nxp.com/assets/documents/data/en/application-notes/AN3461.pdf 
http://theboredengineers.com/2012/09/the-quadcopter-get-its-orientation-from-sensors/
http://multicopter.forestblue.nl/lipo_need_calculator.html
http://www.martyncurrey.com/arduino-to-esp8266-serial-commincation/