My Dutch professor in college actually wrote out the "ij", but the tail of the "i" connected with the "j", making it appear to be "ÿ". It kind of blew my mind the first time I saw him write it out haha
In print, NO. You really can't interchange the two. As already said, in handwriting they may look similar, however we would never mean the actual ÿ, since it simply is something else which is used in Greek and French (and others).
