Is anybody else using these modules, and if yes, what linker script configuration are you using to fully utilize the 4 MBytes of flash? Could you please share your makefile and the linker script file?
Note:
The liker script is set as the LD_SCRIPT variable in your makefile, and should reference an eagle file.
For an ESP-01 module I have LD_SCRIPT = eagle.app.v6.ld located in the SDK folder ( ..Espressif\ESP8266_SDK\ld ), and within this file the section MEMORY{ .. } is of my interest.
Thanks.