Re: Where Did Ueshiba Morihei's Training Go?
Re: left handed and katate swordsmanship.
Every Sat. morning while waiting my turn to practice Jikishinkage-ryu I am lucky enough to watch some very good Yagyu Shinkage-ryu. An unusual feature of some of their kata is switching the grip on the sword to a left handed grip. At a certain point the left hand is next to the tsuba and the right hand is down by the kashira. This allows for some very interesting maai. I've never heard of it being done for any IS developmental reasons.
Many ryu also have one handed cuts within the kata. I think Yagyu calls theirs oni-tachi (devil sword or something like that). There are a number of clever uses of the left hand in Jikishinkage-ryu creating one handed cuts (although not seen in the kata they are there). Katate jodan is also popular in kendo for jodan players as it gives them good maai.
In modern kendo gyaku nito is the most popular, that is the daito in the left hand and the shoto in the right hand. As I understand it it is much easier to learn for many kendoka because it becomes a mix of katate jodan and kodachi kata. Yagyu has sei and gyaku nito in Tengusho (?). Daito-ryu nito is interesting.
I really don't have much time to go into the topic more fully but I believe that Sokaku sensei's nito came from Sakakibara sensei's influence. My theory is that Sakakibara encouraged nito training because it drew crowds to his gekken shows. If memory serves me another one of Sakakibara's student a Mr. Okumura founded a school called Okumura Nito-ryu. Nito kendo was much more popular pre-war than it is today.
None of the arts I know about use left hand, single handed or nito to develop any IS. They are all heiho. That doesn't mean certain skills are not developed by training this way but I don't think it is the goal. I'd be interested in hearing more about nito and katate in aikido.