Hi Daniel,
I would suggest adding a rear line that attaches to the exact center of the stereo bar and can pull the bar back from vertical. This fixes the mics in space better and also will angle them down a bit as you pull back. You can adjust how close the mics are to the performers a bit this way too.
I've seen people even use just thick, black sewing thread. Its usually plenty strong for a pair of small diaphragm condensers (and virtually invisible). Depending on the height you might be able to just tack the back end of the line into the beam further back.
Another advantage to thread is you can throw the spool end to get it up and over high places and the spool acts as a weight so it, sometimes, comes back down the other side.
Good Luck,
Silas