Problem with reversion from 11.7 to 7.31 with CDR

Hello. OS: Suse Linux Enterprise Server 11 SP1 -32 Bit DB: Informix Ultimate 11.70.UC4 respectively Informix Dynamic Server 7.31.UD10X1 We want to migrate our 7.31 Server to 11.70. We tested the Migration with Enterprise Replication to 11.70 a few times and this works fine. To be on the safe side we want to have the possibility to revert the database back to 7.31, in case of a problem in our productive environment. We looked in the official instructions manual from IBM how to revert from 11.70 and we test the reversion such as described, but we encounter an error, when we start the "$INFORMIXDIR/etc/conv/revcdr.sh 11.70 7.31"-Script. Here is the error message (Output of revtestcdr.out): Checking for Replsets statement (select count from replsetdef) failed;SQL error:(-206) The specified table (replsetdef) is not in the database. ;ISAM error:(-111) ISAM error: no record found. But in the syscdr-db the tables "replsetdef" and "replsetdef_tab" still exists since our conversion from 7.31 to 11.70, which completes succesfully. Now the important question: Is it generally possible to revert a 11.70-DB to the old 7.31 Version (with cdr)? In the "revcdr.sh"-Script the reversion to 7.31 is valid, but in the IBM-Informix instructions manual is described, that we could reverse only to 11.50, 11.10 or 10.00. Has anybody experiences relating to revert the syscdr-db to an older version especially 7.31 ? Has anybody hints or tips how we could provide a possibility to go back to 7.31 in worst case? Thanks for your efforts Heinz and Sascha