Like you, I am looking for a medium term (3-5 month) charter aboard a mid 40's catamaran in the Caribbean. I'm curious as to whether you ever found a suitable option. Unlike you, I'm looking for late Spring/Summer which is certainly a lower period. In any case, I've not found any great options though have spoken to Ron at Seabbatticals - however, I'm still looking and wondered whether you'd found any other good sources for these types of charters.