Named storm coverage is available, but it typically adds ~$1,000 or so to the cost of the premium. Talk to your agent. We use Chandre Stemmers
at Risk Benefit Solutions
in South Africa
as our agent. It seems to be a Lloyds policy. Never had a claim so don't know how well they work, but they were recommended by a cruiser who used to be in the marine
Unfortunately, St Maarten is about in the middle of the hurricane
track, so it's best to be prepared.
Not sure why you want your boat covered while it's on the hard. Easier to clean afterwards, I guess, but if a storm does come through, the cover is likely to be shredded. I'd be more concerned that it's well tied down. Multihulls can become airborne in a strong cyclonic storm.