When planing the difficult node sections the blade often tries to dig deeper due to the irregular figure present in a nodal area. If the mouth opening is too great you can ruin a section very quickly. After you align the blade and are ready to start planing, close the mouth to about .020" retract the blade then test plane slowly moving the blade forward until you get the size of shaving you desire. Your first test pass should not remove any cane. Having the small opening allows the plane to support the fibers ahead of the blade and to keep the shaving to a minimal size. So keep your mouth shut and make better rods.