I believe that already the F122 will sail bigger than the Bic 133. If you intend to use sails down to 4.8 on your new board, then I don't think you should go any bigger, especially with 70 kg and a 8.5 as your biggest sail.
You will bump into the law of diminishing returns.
If you want more low end power I do think that F133 would be pretty big already. Its sail sweet spot should be close to your 8.5, and it will start to feel quite big already with a 7.0.
My two cents ...