It depends on the ratio of blade length to wood diameter. I like to have about an 1 1/2 inches protruding so I can be assured that I've got a big enough target.
Regarding flat vs Sabre ground. I think it depends on the blade thickness. Thinner blades baton better than fatter blades, at least that's been my experience.
jerry,
good point. i like a 7 inch blade. the 6 inch just seems to small. the blades i used were 1/4" to 5/16"
