Run unelevated custom action from a WiX elevated installer

Question

I'm trying to figure out how to run a custom action from an elevated WiX installation setup program. The msi file generated by WiX is executed by DotNetInstaller.

In WiX I have a Package section with InstallScope set to perMachine and this custom action:

<CustomAction Id='RegisterPlugin' FileKey='RegisterPluginExe' ExeCommand='' Return='asyncNoWait' Impersonate='yes' />

<InstallExecuteSequence>
  <Custom Action='RegisterPlugin' After='InstallFinalize'>NOT Installed</Custom>
</InstallExecuteSequence>

Impersonate set to yes should run the action exe as the user who run the DNI bootstrapper. The custom action should read a file in the user AppData directory, using the value obtained by System.Windows.Forms.Application.LocalUserAppDataPath, but the directory used is wrong because is the one of the Administrator user.

I tried to use a manifest to run DNI unelevated, but the problem remains. If I run the msi directly, it correctly does some registry operations which require administration rights, while the custom action runs as expected.

Edit: Looking at the task manager I can see that, if the msi is executed from DNI, the user becomes Administrator when the msi is started. If I run the msi directly, the user is always the same, even during the files installation on the system directory. It seems that in this case what change is not the identity, but the privileges.

Any ideas?

Thanks, Stenio