Hey -
To set it up exactly like the UE3 model, you will need to set the B input of the Add node after the Mask (B) to 8 and the B input of the Mulitply node to 0.8. Make sure your falloff texture is Texture2D'/Engine/EngineVolumetrics/LightBeam/Materials/T_EV_LightBeam_Falloff_01.T_EV_LightBeam_Falloff_01'
Let me know, that should fix it up -
Eric Ketchum