I'd go with a 20' and an offshore mount too but unfortunately an 18' with a transom mount and a swing away tongue is about as big as I can get in my garage. Nowhere else to put it. The 18' has been a good compromise for me, but I dont think I would go any smaller. I see guys storing their boats outside but there has been a rash of motor thefts going on around Seattle. The meth crowd will steal anything.