Al -- I've responded to your email, but there's another potential hint for your Maas research that I've indexed (see my first published volume this summer ;-)
Since we've confirmed that John Maas was Johann Philipp Maas, I have index entries for a "J. P. Mass", who was a mason by trade and had a letter held for him at the post office in July 1860. The letter was postmarked from Schönberg, and was due to be returned there (the letter is not archived).
That's the kind of hint that you may see matched in another record - even if spelled badly or differently.
And is a Maas / Mass spelling variation any more of a surprise than the variations of Zibolsky Zibolski and Zibolske found in the German papers? (Carl's name is spelled Zibolski in the German papers.)
That's the kind of research detail that local researchers and lib'arians glean from my postings to present as their own original research!
Milwaukee's German Newspapers; an index of death notices and related items; 1844 ...1950 / an ongoing, independent project created, compiled and edited by Gary R. Rebholz.