Limbing spruce or balsam fir will lead to stem and butt rot. Also what tends to happen is the saw gets run too close to the stem and shaves the bark up and down. Not a recommended treatment at all. Grow your softwood close and let them self prune, then do a semi-commercial thinning at age 30. If you can't resist the urge to prune than make sure you leave enough on the branch stubs and not cut into the washer-shaped swelling at the base of the branches. Pruning can be successful in pine and hemlock if done properly.
cheers
