I just sold my Marstrom A-class with gennaker, I got an offer I couldn't refuse. My plan is to buy a new Marstrom during the spring and that boat will probably have "banana boards". Marstrom are working on moulds for the boards right now. I will of course fit the boat with the spi snail that I will use for distance racing. Marstrom has a smaller snail now designed for the 17 m2 size of gennakers instead of the M20 version I've been using so far.
The majority of the A-class sailors seems to think it's ok with banana boards and then it's just to follow the class or change class. I decided to stay in the class and upgrade boat. Older Marstrom boats can probably be rebuilt to handle "banana boards", more news about that later when I have facts.