There are quite a few "gotchas" with the client side piece of this. The first is HP's MSI for the client. It installs to "C:\Program Files\HP\Quality Center Client Side". But the docs (and testing with an upgraded server) clearly indicate that the server will push updated files to 'C:\Program Files\Common Files\Mercury Interactive\Quality Center'. So if you install HP's MSI to its default location, it will fail.
Also, the HP docs indicate that although it requires administrator permission to install the client, restricted users can 'start' it. The doc then goes on to say that 'you' (you the installer? you the restricted user?) need to have permission to a variety of file system and registry locations.
Our experience with QC since 8.x has taught us that the vendor provided installer for the client doesn't quite work. It has also taught us that when a user logs into the server, the server pushes down updated DLLs, ActiveX components, etc., and tries to register them. This will fail as a non-administrator user.
Even if you package what the server pushes down and build your own MSI from that, it will fail when the server tries to update something.
The solution, we've found, is this...
First, start with a clean machine that has only the pre-requisites for the client installed. Start a snapshot (SetupCapture in Wise Package Studio) and get your 'before' image.
Then, connect to the server and let it push the entire client down to the desktop. Complete the snapshot process to build your initial MSI.
Adjust the MSI so that the user has permission to re-write every file the MSI installs.
Export everything captured in the HKEY_CLASSES_ROOT section of the registry. Using a text editor, modify the resulting .REG file so that HKEY_CLASSES_ROOT is changed to HKEY_CURRENT_USER\Software\Classes. Reimport this. Configure ActiveSetup to deploy this to each user.
Modify permissions on the HKLM\Software\Mercury Interactive key so that users can modify that.
What you should find is that you can deploy this new MSI to end users using administrator permission, then they can run the client using a restricted account. If the server attempts to update the client, that's ok. The user has write permission to the files involved, the HKLM area used by the package, and a copy of the DLL/OCX registration information in their HKCU area that they can also modify. From here on, the client should work perfectly.