Answer:
No, unfortunately this is not possible.
If you save the last position of your model in RFEM or RSTAB, it is done in the currently used version.
However, you can also open RFEM 5 files in RFEM 4 and RSTAB 8 files in RSTAB 7. In this case, please pay attention to the notes in FAQ 004112 by clicking the link below.
