JDBC4 Binary Mode with Arrays

Sorry for the cross post, I put this on general first:

In my current application I am sending a lot of data to/from the DB with JDBC, and specifically arrays of Double. (or even Double[][]).
I have been converting everything into a string representation of the array with StringBuffer, which eats a lot of memory.

I note that there is this web page:
http://wiki.postgresql.org/wiki/JDBC-BinaryTransfer

Which made me think I might be saved.

After trying out the JDBC4 driver in DBCP, I see that Connection.createArray(...) still just creates a big string under the covers. Is that the expected behavior? Am I doing it wrong?
Will the String get converted to binary representation again before hitting the wire?

Regards,
-JD