I cut a peach last year. It was about 3" in diameter so I cut out the belly side and strapped it to a form for almost a year. When I took it off the form I took the belly side down a bit and it felt nice and dry.
With your staves that are bigger I would split them in half(or saw them if they didn't grow twisted), seal the ends and give them time to dry. They are big enough in diameter that they shouldn't twist or warp.