The Stubby 99 is a great waveriding board, with reasonable planing/speed. But not really a board I would reccomend for B&J. The Grip will be better as it´s a bit wider and has a faster rocker line, so it should actually plane earlier than the Stubby, especially when the wind drops, as the Stubby is fairly "narrow" in the centre in the 99 size vs other 100L boards. Should feel fairly similar to your 89, but obviously bigger.
But for B&J conditions, I would actually say go for a FW95, this may be the ideal board for you, the 2020 models are a great upgrade. any chance to test them, I see .se, maybe at Surfers?