Sonic adventure 2 DC question

....i'm not sure if i've asked this elsewhere...but here goes!..

I have a backup of sonic adventure 2's files on my hard drive...what i want to know is, can the files used for the game charas (sonic/shadow etc...) be swaped around (file renaming), thus getting shadow on sonic's stages and vice versa..?

if this can be done......?

and if so, what would i need to use, to make the back-up a selfbooting game again? (i'm on XP and all the selfboot tools i've tried don't work...OR is there another way round this....?)

thanks in advance!

I thought talking about Dc backups was a no-no....

Anyway, you can switch up songs in certain games, I've heard of it done before in Crazy taxi (thank god, that song, over, and over...) and games like marvel vs capcom 2, I saw the documentation somewhere and can ask for it if you want it. Of course it won't work for all games (Samba de Amigo and Rez in particular I assume) and Im not sure for SA2.