A user, Firoball most likely, once tried to convert old A3 maps into A7/ A8 maps, a few years ago. I think he did that by writing a self made tool. Wait...

http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=374797&page=1

Seems like that was the beginning of his endeavour. Are you aware of that thread and the following posts (over a few weeks I guess)?

"Falls das Resultat nicht einfach nur dermassen gut aussieht, sollten Sie nochmal von vorn anfangen..." - Manual

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