Mounting this from underneath the console should probably have been a two person job, but daisy_knotwise was picking up dinner when I started and picking up the last of the stuff from the floor in preparation for the cleaning lady when I finished, since I snuck a bit of time after dinner to finish up the job. (There comes a point during the cleaning when I start to become superfluous. And there was laundry in the washer that needed to go in the dryer about then...) The positioning is not yet perfect, but I'll check out the website for the manufacturer of the arm and see if I can get a couple of tips on how to shift it around to exactly where I want it.
In the meantime, it looks pretty much like it was meant to go there and the studio is put back together, so I'm going to count this as a success. :)