Maybe this would be less bad if the reflector was in better shape, and/or by playing around more with the centering gasket.
Do keep in mind just how abused this reflector has been: face ground off, orifice drilled out, orange peel polished away, dented when my bench grinder shot it across my basement, etc. 
Edit: With a piece of #3 film the beam looks perfectly fine, and still has more throw than a stock TS10. It did reduce throw somewhat, though.