Have you found anything about your STIMAC ancestors? I recently did a seminar for St Nicholas Croatian Byzantine Church in Cleveland. Most folks from this church are from Zumberak area of Croatia. There are many STIMAC in that region both Byzantine Rite and Roman Rite Catholics. Let me know if you need some help in locating info.
Croatian Heritage Museum
PS Lower Austria was not the area that is now Croatia and Slovenia but was actually to the north.