I recently had a job that I was doing and tore everything apart to find 16 ft. runs with no middle support and very little on each end, ( VERY SCARY ) . I considered using a piece of steel for a ballast beam, but I searched YouTube for an alternative way to install a beam and stumbled on this video. This video gave me a great idea on how to make and install a support beam without killing your back and hiring a big crew to help install. Granted the beam I installed was nowhere as big as this one, but it did the job and remove the sag out of the floors. If you are not comfortable or unsure, you can always higher an engineer. My method if I am unsure, is to build and support it to the extreme and don’t take no shortcuts.Take your time and think of every possible situation that could make it fail, and when you have completed the project, test it by trying your best to make it fail. If it doesn’t fail and still holding strong, then you are done.