Installing Trinity in Parallel with KDE 3.5.10

How is Trinity installed in Kubuntu to allow running Trinity or KDE4? Slackware uses two primary run levels: 3 and 4. Run level 3 uses a command line login and starts X and KDE 3.5.10 from the command line, through /usr/bin/startx, /etc/X11/xinit/xinitrc.kde, and /usr/bin/startkde. Run level 4 starts X through /usr/bin/kdm and that is where users login and run /usr/bin/startkde. Building Trinity to install in /opt is no problem, but running either Trinity or KDE 3.5.10 from the same system in run level 4 is not so straightforward. For run level 3, all I need do is create a new xinitrc file named xinitrc.trinity. I can make that the system default or let each user account make that the default. Easy enough. Run level 4 seems a tad more complicated. I can add the Trinity version of kdm (opt/trinity/bin/kdm) to the system rc.d/rc.4 script. I can add a second Xsession script for the Trinity version of kdm to ensure the Trinity version of Xsession is used. But at that point users wanting to run or test both Trinity and KDE 3 5.10 on the same system seem stuck using either the KDE kdm or the Trinity kdm. There does not seem a nice way to toggle the system unless I modify the rc.4 script to ask the user which kdm to use. A login manager should be desktop environment-neutral. I'll guess there is no damage in using either version of kdm to launch either Trinity or KDE 3.5.10. Yet perhaps there might be problems because of the libraries loaded into memory. I'll guess that Kubuntu avoids the problem because the default login manager is gdm. The stock Slackware does not come with gdm or gnome. Then again, possibly Kubuntu uses the KDE4 kdm as the default login manager and that avoids library conflicts too. I hope I'm missing something obvious and simple. :) Thanks. Darrell