You want to be very careful using a boring head as a flycutter. A boring head is not made to take the load that a flycutter does. Years back, we were making some panels for the Paris Air Show, and one coworker who was also a Tool & Die maker was using a boring head as a trepanning cutter. He was popping some large holes in .093 sheet aluminum. He made it through a couple holes which relieved the sheet stock some, and the cutter caught when the sheet flexed. The boring head grenaded all of the parts of the head.
So if you are using a boring head as a flycutter, just make sure you take very light cuts. And better yet, make a flycutter and save the boring head for the precision work.