This has been figured out and posted by TeamEurope in 2012 (link, link via link). Unfortunately, the original document has vanished from the WWW. I’ll try to recreate this tutorial here:
The original document suggested to use Sesame Street: Alphabet Avenue as donor cart and pointed out to use an „Assembled in Mexico“ cartridge. As you can see, a regular US cartridge won’t do the trick.
Continue reading Sega Pico Flash Cart Tutorial