17" wheel fit on standard Beetle with 18mm Adapters

[Mexibeetle]

OK, I have read through just about everything here on whell fitment but seems that everyone either is doing this on a Super or has a norrowed front end. Also I see comments about ET 40 fitting perfectly and ET 50 or ET55 Porsche wheels fitting. This doesn't make sense that bot ET40 and ET55 fit. I have a standard beetle ball joint front end with discs on fron and drums on back all stock. I have a 4X130 to 4X100 adapter from a 914 that is 18mm thick and am trying to find out what offset on a 17X7 would fit under stock fenders. I have spent hours researching but it seems everyone else has widened fender, narrowed front end or some other modifications. Any help would be appreciated.