1616 showed a good diagram. the bungee pulls the cars outboard, not inboard. You don't need the bungee, but you do need the outer turning blocks with some mini cleats.
We would cut the stop pin off the car and put it back in the track, inboard of the jib block. You can set the stop pin more out board for strong wind so that when you release the out pulling line from the cleat the jib block slides inboard, stopping at the stop pin. Other wise you have to pay attention to where you cleat off the jibcar for the next beat.

Your question about the mast base is rare. i didn't think a dolphin striker post could strip the treads of a mast base. They are generally fused. Anyway it's not a problem while sailing, the super cat 20 had a free floating dolphin striker post. It pushed down a couple inches under load.