Today I spent some time with a trivial task. When you forget to call Wire.begin() bad things happen when you try to use I2C.
Anyway, the code now reads the Y acceleration from the MPU and I built a table of slope % as function of Y-accel.
The LCD display was helpful in this and I am glad it worked. Now it's time to build a BLE service around this and start publishing values.
Code in github is up to date.