Tanja;
Karlsdorf was in the Banat Military Frontier and the inhabitents were Grenzers who served in the XII Deutsch Banater Grenz Regiment.
Tracking Grenzer families in the Frontier can be a bit more difficult because these guys were frequently transfered from company to company. Since each company was associated with given village it sometime happened that a person would be born in one village, be married in a second and have kids born in further localities.
There are now family books available for five different localities in the Grenzland, Homolitz, Brestowatz-Ploschitz, Startachowa, Pantschowa and Apfeldorf, all by Adelhardt.
Firstly the work by Emil Maenner(Suedostdeutsches Archiv III 218(1960)lists the orgional settlers of Karlsdorf with data taken from the Karlsdorf church books(KBs). There is no Schaab listed but among the orgional settlers was Johann Kremer, wife Anna NN, *ca 1736 Mettnich=Primstal, Kr WND(SL), + Jun 1804 Karlsdorf.
The Ploschitz family book, covering the time spann 1766-1835, lists;
Schab, Michael, Neuansiedler from Auerbach/Wuerttemberg
oo
NN Anna
+25 Jul 1791 Ploschitz from Auerbach/Wuerttemberg
The Homolitz family book has a single Schab entry as follows;
Schab, Valentin from Karlsdorf
+vor 1944
oo
Schmitz Elisabeth from Karlsdorf
+3 Jul 1943 Homolitz
kids
Rosalia *19 Mar 1893 oo Franz Preisach
Katharina *31 Dec 1895 oo Johann Steidl
Theresia *17 Jun 1898 oo Josef Horwath
Finally there is an Anton Schwaab, age 20 listed in the 1798 Revision lists of the XII Deutsch Banater Grenz Regiment(See FHL 121713

which gives his birth place as Ploschitz but Musterplatz Kubin, HN 5.
This apparently is not totally correct since Anton Schwaab's birth record is not given in the Ploschitz family book.
It would be helpful to know if this Schab family was Protestent or Catholic. If Catholic one could exclude Protestant places like Franzfeld and Mramorak from consideration.
Dave Dreyer