When I use a stave with that much twist I cut them in half remove the twist, now 45 degrees instead of 90 in each billet, and splice them back together perfectly orienting the backs to be in the correct plane. Sounds like a lot of work but I think it is less than taking 90 degrees out of a full length stave. Excessive untwisting can cause some tiny longitudinal fracturing in osage, not fatal stuff but visible.