Where to put TQt3 when replacing Qt3?

Guys, Gals, When building TQt3 to replace Qt3, what is the name for the recommended install dir (i.e. $QTDIR)? I am going to put it in /opt, so should it go in: /opt/TQt3 or should I use it as a direct replacement and put it in /opt/Qt3? Specifically, I am attempting this on archlinux where I have only used Qt3 before. Is this advisable, or should I just stay with Qt3? If I install TQt3, then will updating /etc/profile.d/qt3.sh be the proper way to tell the rest of the system where to find Qt3 --or-- should I create a new profile named tqt3.sh with that information?? -- David C. Rankin, J.D.,P.E.