I bought a couple ArduPilot w/ ATMega328 boards a few years back, but didn't get to use them .... work got in the way!
I'm still keen to do something with them -- using an IMU set-up - but now that ArduIMU+ V2 (Flat) is no longer available/produced (understandably as much as changed since I bought my boards) it seems that 3D Robotics Inc's ArduIMU+ V3 kit (or the board from SparkFun) is the only IMU available.
However, I have read that it isn't compatible with the ArduPilot legacy board despite being pin compatible. Can anyone shed some light on this? It seems strange that it isn't as SparkFun bills it as a replacement for V2!
....look forward to receiving some advice.