000:
@ nick
Tried uploading larger sketches?
Not yet.
and Is the bootloader uploaded by your arduino_sketches/Atmega_Board_Programmer at master · nickgammon/arduino_sketches · GitHub same as the one provided by maniacbug?
It is the file optiboot_atmega1284p.hex from maniacbug's GitHub page. Slightly modified to change some of the consecutive 0xFF bytes to be 0x00 because of the problem with uploading a lot of consecutive 0xFFs to the Uno using the standard Optiboot (known bug there).