Is it possible to 'custom' install a SAP GUI patch?

Am I right in thinking that if a client has GuiXT deployed and he applies a patch, GuiXT files might be overwritten? What can we do in such cases? Also, I am not sure if GuiXT.ini is overwritten.

When you apply a SAP GUI patch, recent GuiXT files in the sapgui folder are not overwritten. The guixt.ini file is also retained.

If you want to keep an older version of GuiXT, you have to copy guixt.exe and guixt.dll again, after applying the patch.