George S. Ledyard
Most Aikido practitioners who do weapons, especially sword, cannot adequately tell you how what they do directly ties into their empty hand. To my mind, if it's aiki sword or aiki jo, then the principles at work are identical to those at work in the empty hand. One should delineate what those are. If not, then probably what is going on is a bunch of "stick whapping" and really has no relation to the empty hand.
At a seminar I taught once, I was breaking down a set of Saotome Sensei's forms at a level of detail that the attendees were clearly not used to. One stated that he wasn't doing sword to actually be a swordsman, he just wanted to make his empty hand better. I challenged him to tell me how doing bad sword could possibly make his empty hand better.
Totally agree, however I question the idea that "real" swordsmanship improves aikido more than properly understood Aikiken. I believe, from experience, that many aspects of unarmed combat derive from lessons learnt in armed combat, most importantly that survival is often measured in a "hair's thickness". Precision, timing, distance, rythym, postural alignment, focus, relaxation, etc., etc.
I also agree that "stick whapping", whilst lots of fun for the testosterone impaired, bears little relationship to empty hand, it also bears virtually none to swordsmanship. Thus I can only conclude that those who don't learn much from aikiken would probably not learn much from working with a shinken. Those who are serious, shin ken, would learn with a chop stick.