I've flown the spinnaker on the Tiger a few times in mid to high 20s, with gusts up to 30 knots. At this point you have the boards pulled half way up and are sailing deep and not trying to fly a hull. It feels reasonably controllable - I feel more scared when trying to turn down wind in those conditions.

I think the stress on the rig is less under those conditions than when you reach double trapped with a spinnaker.
Chris.