I've done the SXM to ANU and back passage more times than I can remember. The actual sailing portion is only 100 miles and has never taken 24 hours. So your trip will have to include stops or anchorages - perhaps St. Barths or St. Kitts/Nevis on the way. With that size boat, I'm assuming that the captain wants/needs a crewmember for watches so I'd just share costs for provisioning and clearing in. And clearing into French St. Martin is 5 Euro.