(Tony Rey discusses jibe-setting in a large fleet in a story posted on the Sailing World website. Here's a brief excerpt.)
The right time to jibe set is determined by how bad you think the disturbance will be on the top-right side of the course. If you are in the lead pack, then there will be more bad air to jibe through. You need a really good reason to sail back through that mess. If you are deep in the fleet, it will be relatively clean to jibe right away. However, the jibe set becomes more risky when the wind is light, because not only are you sailing through bad air, but also disturbed water (which can sometimes be worse). I generally stay away from jibe-sets unless I am laying the leeward mark with a quick jibe, and the initial pain of bad air and disturbed water is worth it.
However, a really nice move to have ready is the 'quick jibe'. Often the decision of when to jibe can only be made in the moment (depending on exactly where the cleanest lane will be behind, and what the boat in front of you does), and you want to be ready to either hold on starboard, or jibe. The quick jibe is when the boat is setup for a standard bear away set, but the helm just turns the boat into a slow jibe, the kite is rotated around, and the pole is tripped away. Your trimmer and pit person need to be ready for this. - Sailing World website, full story
