Hmm, just had a look at my 7.5.3 install files and I think they are the same. This is the CD / network install image. My System 7.5.3 01of19.smi file has a type of "APPL" and creator "oneb". If I double click it, it "mounts" the CD image (by checking all the other parts are there). Doesnt look like you need Diskcopy 6 for this - sorry, must of got that confused with something else I was doing
That transfer process sounds ok tho.