For what its worth - my opinion:
1 On San Francisco Bay where the wind howls in the summer but there are many wind shadowed areas, we have found the staysail to be useful and easy to use. On departure we put one reef (at least) in the main and then roller furl the jib from the cockpit as required for the variable conditions. I would not give up my staysail, it just makes sailing that much easier.
2 As long as you are attending to the car I would make an improvement over what is shown in the attached picture and provide for remote adjustment of the car position. This would greatly facilitate getting a good shape into that sail.