Hi Werner,
I did not know about this "-f" option and I did not check the remaster howto for quite a while.
In all cases yes it does make sense to use the -f option to lower the RAM requirement even though
I did not try it yet, but I will for sure use it in the near future, as well as the -L -1 (for lzip compression).
Thanks for the suggestion ,
Best Regards,
Gilles

PS: the help option for "create_compressed_fs" is "-h" (instead of --help)