Bill, after over 60 boxer engines in 14 month, believe me, it work! even if
your theory make sens, still, wasser wear with gravity, from bottom to
top... oil will seal the lower part. but over all, my theory is that wasser
are a better design than upright I4... an old mechanic told me that the
pistons always "seat" comfortably on the cylinder bottom on a nice cushion
of oil... a good example is the venerable Goldwing Honda flat 4 engine....

But anyway, that is just a theory!

Regards, Ben
http://www.benplace.com/vw2.htm