I think 4 staves is safe, if any more maybe 1 depending in my experiece, assuming 7" on the big end.
Read the log, looking for natural checks in the end grain you can exploit on the first parting. Look along it's lenght and envision where your split could run, bearing in mind it's gonna always follow the grain, and ain't gonna run through a knot. You can use a small hatchet to help direct the splits, and definately to help cut out the "stringers" as you progress. If you don't, they'll influence how the rest of the split runs.
If you debark, do it after quartered and once you expose sapwood get it off down to heartwood. Then seal that (heartwood) as quickly as practical, even if just an overnight for exmaple.
Post pictures.