In the end, the winds that I used the flying jib in were not that much stronger, only up to F3. However, it confirms that the sail is a very useful one to have. It appears to lift the bows and on a beam reach, I was doing 4.5 knots over the ground in 7 knots of apparent wind, although I may have had some help from the tide. It certainly felt fast for the wind conditions, perhaps adding as much as a knot compared to the three-sail setup.
Most important of all, it is easy to handle solo. Previously, I needed crew if I was going to fly my asymmetric off the spinnaker pole but the combination of a flying jib and tiller tamer apparatus makes the whole thing child's play, at least in lightish winds. And because the BR is so easy to sail solo under three sails, the addition of a fourth gives me something to play with in conditions that might otherwise be a bit humdrum.
The sail was made by Hyde Sails to Matt's design, adding 3.4m2 to the existing 17m2 sail area. Cost was £230 + VAT. Of all the mods and changes that I have made to Turaco, I think this one is at the top of the list of big ticket items in terms of bang for the buck. It will be getting a lot of use in Corfu, where morning winds tend to be on the light side before picking up in a fairly predictable manner during the afternoon.