30. Never under estimate the need for storage and how the storage is laid out. In other words are the things I put in there going to shift around to where I can't see them or get to them without standing on my head. And number 4 is really important, you need to be sure you have a jack and a lug wrench that will fit you boats lug nuts. More than once I've stopped to help someone change a tire on their trailer and they have a spare but their car or truck jack and/or lug wrench won't fit the trailer.