I've seen several versions of a dust box behind the fence that looks promising too. Basically you build a box around all of the interferences behind the fence, put a hose on both ends and then cut thru it with the miter saw blade.  They look like the best solution.  Anything is better than my current set up - blowing the dust all over my daughter's basement.  MDF trim makes it even worse.  Miter saw, table saw, router table, drill press are all on the list of tools that absolutely need attention to get better dust collection once I get a few minutes to work on shop projects.