My Nacra beach cat has 10 full length battens. Very common with this type of boat. Batten tension is an integral part of setting up the boat before each race. Quick adjust batten caps are a must. The easiest way to set them is to tilt the boat over on its side so you can sight down the leech, observing the draft, as you're setting the tension. It just takes a few minutes to do this. The flatter you want your sail.. the lower the tension. Which also gives you a wider adjustment range. Increasing the tension will force the sail to maintain it's shape in fluky or light air conditions, but offer a smaller adjustment range. The older nacras use a "tapered" foam core batten that allows it to bend more near the luff and maintain greater stiffness at the leech.
In the type of competition Jackdaw participates ... I would imagine some attention is paid to batten tension at the beginning of the race day when the main is hoisted. Maybe even between heats if conditions change drastically. The few times I've raced my Catalina, with just two full length battens.... I've not paid any attention to them at all because I've always left them fairly loose... they're there just to support the leech, not shape the sail.