I mounted mine under the desk, by drilling a couple holes in the top of the mounting bracket and screwing it to the bottom of the desktop. Used velcro only long enough to decide where I wanted them, but the Velcro doesn’t hold them steady enough, so the screws worked great.
Later in the build (once my Bravo Throttle arrived), I stacked my two radio panels and one multi panel on top of the Alpha and Bravo units.
Jim-Sim
Edit: There are some additional ideas in this thread: