Using MacPorts to install to another directory other than /opt/local/bin

Using MacPorts to install to another directory other than /opt/local/bin

I'm having a problem of consistency between my machines because I have to explicitly specify the command path for some items like Image Magick. Port installs them to /opt/local/bin, but for consistency, I would like to install to /usr/local/bin. How can I specify that?