Steve,

I've never sailed with a spinnaker so can't give you advice on your problem.

I would imagine however that once the wind got to 15knots it would be time to drop the spi for a beam reach. The boat would pretty much be at hull speed by this stage and the spi probably won't get you to go any faster wheres the risk of disaster would be quite high.

As I say I haven't sailed with a spi so may be completely wrong.

Can the Mozzie mast handle the spi OK?

Rob.