Load plug-ins in embedded mode

Hi
I have an issue with this feature on x64 bit OS.
The plugin we are using is Thinprint and here is a installer for 64bit os http://thinprint.dkvistun.is/9/TPCLWin3290x64.zip
now i add a registry key for it to work with C:\windows\syswow64\mstsc.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Terminal Server Client\default\AddIns\ThinPrint
New string Value : Name
Value : C:\Windows\System32\TPClnRDP.dll

Now if i use mstsc 32bit and mstsc 64bit Thinprint gets loaded but is does not get loaded in embedded mode in RDM

Best regards,
Valdi Hafdal