Re: KD8CEC firmware v1.2 with factory display
The answer is no, there is not enough room in the KD8CEC firmware to allow for the screen painting that the stock display requires. The KD8CEC firmware works with one of the text displays or one of the Nextion displays. The text display is a simple interface, and the Nextion graphics display has its own processor for heavy graphics manipulation.
There is a 2.8" Nextion display that fits in the stock case with only a little bit of filing on the display hole. there is also a Teensy Raduino board available from others that can drive the display and has reserve processing capabilities that you could add more features through software.
At a minimum, I would look at either Reed N's firmware or N8ME software that can be run with the stock hardware. They correct some issues with frequency scrolling and CW operation. They are free and can be found in the files section of this reflector for the N8ME or GitHub for Reed N's