To prevent an alternator bracket from breaking on your wasserboxer try this:

1) when installing alternator, check mounting surfaes and make sure they are
parallel and not worn on one side.
    ( if so grind flat with dremmel )
2) install shims between the alternator mounting points on the bracket to
minimize stress on the bracket.  ( I used rocker arm shims ) But spring
washers work as well, they look like they are warped and are thinner,  not
as accurate, but they still work.
3) loosen the lower bolt on the long skinny bracket so that it will not
inhibit proper tightening  of bracket
4) install alternator with shims, it is best to use a nylock washer or use
loctite 242 ( blue stuff ) to keep it tight, but don't crank it down just
yet
5) install top bolt from skinny bracket to alt and put proper tension on
belt, tighten the top bolt on the alternator.
6) tighten bottom bolt on the skinny bracket where it meets the case
7) tighten the long bolt beneath the alternator.
8) check pulley allignment and you're good to go.

Malibu Tony  85' Westy