PersistStreamType defines how the security descriptor is stored into the stream. If this value is true a flat memory model of the security descriptor is directly stored into the stream. On the other hand if this value is false the LoadFromStream and SaveToStream of TJwSecurityDescriptor will be used.

if PersistStreamType is pstPlain the stream layout is the following:

  [0..3]      size of descriptor
  [4..[size]] realtive security descriptor (as in memory representation)

To get the layout in case of pstJWSCL check TJwSecurityDescriptor.SaveToStream 

The layout in case of pstIAccessControl is unknown. 

Be aware that this stream implementation is propably no compatible with the IAccessControl implementation of MS.

TJwServerAccessControl Properties