If you have the space behind the saw, I recommend you consider a different approach. Put the saw on the bench or better yet, raise it up and mount it at the back of the bench. Use raised "shelves" on each side to support your boards.
I mounted a slider like that in my old, tiny shop and it worked great. The slider could slide back into a recess in the wall - I converted a window into a window box just for this purpose.
The main reason for doing this was I never had to clear off my bench top to cut boards on the mitersaw. If your benchtop is the surface you set the boards on when you are cutting, then you must leave it clear all the time. Two additional benefits of my raised shelf were that boards were closer to my eyes so it was easier to see pencil marks and I put drawers under the raised shelf which I built like a torsion box. If I get a chance I'll upload a pic from my old computer.