To do a private, SxS install, see:

http://msdn.microsoft.com/en-us/library/ms997620.aspx

I once made a private SxS installation of a MSVC-reliant app (that you
could install with non-admin privileges), and if recall correctly, it
required disabling the generation / embedding of the manifest file in
MSVC++, and then include the MSVC dlls and hand-edited manifest files in
the installation.  (Or perhaps you could somehow edit the options for
the embedded manifest's generation? never tried this myself...).  (Or,
if you don't like .manifest files littering the install directory, turn
off the auto-generation of the manifest, but embed your own hand-edited
manifest as a resource.  I'm sure this is possible, but figuring out the
exact steps to do it may be more headache then it's worth...)

I don't remember exactly, but I think in order to make a manifest that
worked for non-Admin install, I think all I had to do was remove the
'publicKeyToken' property from the assemblyIdentity... if it's present,
I believe it tries to find a registered, "signed" version of the dlls -
and registering signed SxS dlls requires admin privileges.  What I don't
remember is, if 'publicKeyToken' is present, if it just gives up if it
doesn't find a signed version, or it simply means that it will use a
signed version preferentially to a 'local' copy if both are present...