I wrote a new handy script (install_1013_DP2.sh) which downloads the individual upgrade packages for macOS High Sierra DP2 (17A291j) from the CatalogURL and then the installer opens, right after the download has finished, and it let’s you pick a target volume.
I myself even ran the script from macOS Sierra 10.12.3, after modifying the ProductVersion in: /System/Library/CoreServices/SystemVersion.plist which I changed into 10.13 I restored the value (10.12.3) when the installer started to move files.
Edit: In case that you don’t have a RecoveryHD, then you will see an error at the end of the installation procedure. No worries. This is expected behaviour.