I dump all the overlay.bin, and i uncompress them with crystaltile. Then i open all and i wrote all the .c functions that i find.
Then i used desmume debugger to find the called file. During emulation into slow VRAM part((200000-300000) the game load first the function and after(it's not easy to find) the file used from the function. I don't know if all the function work at the same way, but for now all the called file are exact.( For example zonedata.c called a 0 1 2.narc that contain effectively the map properties list.)
Do you wanna help me in this research?