[CentOS] how to enforce sunit and swidth for root device/partition when installing?

Hi,

how can I force the Centos 7 installer to use the particular sunit and swidth values that are matching the hardware raid device I´m installing on?

The installer forces me to reformat the partition I want to install on :( It does not let me specify any options about creating the file system :(

Even when I create the file system manually with correct values after telling the installer where to install and before beginning the installation, xfs_info shows different values for the file system than I used when I created it once I rebooted. So apparently the installer re-creates the file system again when I start the installation after it had me accept the changes it wants to make.