There are some BUGs in the source code of these files...
1. I strongly recommend to use the same DataBase prefixes. (old shop and fresh shop). I had to update all these files manually inserting different prefixes.
2. There is difference between old language codes and new language codes... in ps_lang.
New PS 1.6 have language code for example de-de
Old PS 1.4 -> updated to 1.6 wiil have de language code...
3. some updates to copy_shopdata.php
line 62 for($i=0; $i < (sizeof($oldlangs)-1); $i++)
we should reduce count of iterations.
line 207 for($i=0; $i < (sizeof($oldlangs)-1); $i++)
same