In making hardwood shafts, I'm finding that I can use less spine with those than softwoods. For example...I'm shooting a 60 lb longbow...and need 55-60 lb softwoods...but need only 45-50 lbs in hardwoods. Go figure. I think they recover more quickly. (When I use a 60 lb hardwood, it's overspined and doesn't fly straight).
Kevin