Quite a few programs install into /usr/local/ABC, but not all of them do, unless your package has a completely unique directory structure, Why not place binaries in /usr/local/bin(or sbin), man pages in /usr/local/man.. resources or default data in /usr/local/share/ABC/*
As for user specific configuration files, create a hidden directory in the users home directory... /home/user/.ABC/*
That's pretty much a safe default for most software, the whole /opt + FHS thing is so Linux-centric..
