Installing KDE3 and Trinity concurrently

Is anybody installing KDE3 and Trinity concurrently? Specifically, both desktops are installed to the same partition set and as appropriate for the respective distro, users can select between either desktop environment? This requires installing both desktops in different locations, such as /usr and /opt/trinity, or /opt/kde3 and /opt/trinity. I run both desktops and use KDE3 often to compare/debug Trinity issues. I do this with a separate installations and virtual machines. I would enjoy being able to install both desktops to the same partition set, but I run into serious menu problems that I haven't resolved. Being able to run one user in Trinity and another user in KDE3 for testing would be much better than using a VM (VMs have some limitations). Thanks much. Darrell