I finally got chained ADS1115 encoders working to read arm bone positions. It was really confusing because the manual lists configuration setting bit offsets in low-endian, but the chip then accepts the resulting bytes in high-endian (reverse) order. Code here:

https://github.com/01binary/drummingrobot/blob/master/src/code/ads1115.cpp

The breakthrough came after I took the Raspberry Pi with me hiking and stayed at a countryside hostel for the night, debugging into late hours