Let me post this how-to, principally as reminder for myself
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The steps to use X: as ramdrive and for the user profile folder instead of ramdrive B: are:
(x)EnvironmentPE
Location:Sistem Drive (with packuser.exe)
(x)RAmdrivePE
Create RAM Drive when needed for User Profiles
Drive and File System B:
(x)Programs FilesPE
Location:%SystemDrive%
(x)Create ISO
(x)Use File Based Write Filter. Use Files from: