hmm. you dont want to cut into your door panels, but want 6.5s. cant have your cake and eat it to - ya know? lol . I think that you might be able to construct some sort of unique brace/adapter out of MDF (wood) that will allow you to sit a 6.5" diameter behind the 5.24" cutout.... now that'll probably push you're speaker magnet too far back into your door, and require you to cut out some metal behind there. both ways, looks like cutting is involved.
to be honest, dont listen to me. I really shouldnt say anythign about fitment unless i look at the inside of the door and the speaker being installed..
this was just a bit waste of a post.