I've realized that the model addition wasn't showing up because once i create it it would take on the same scale and opacity as the photon cannon.
I've unchecked all accepted and inherited property values on the model addition however it still inherits all the properties of the original model. any suggestions?
edit- I went to the model additions events and added: Actor Creation>Set Opacity 1, and Actor Creation>Set Scale 10. And that made the model addition visible and full scale. Fixed all my problems. Thanks for you're help and views hope this helps anyone else who runs into these problems.