I look forward to your conclusions about the purported link with Shugendo, Peter. The only connection between Daito Ryu and Shugendo I'd heard before was the founder of Hakko-ryu, Okuyama Ryuho, joining a Shugendo sect . . . but this was after he had studied DR (to whatever extent) with Takeda Sokaku.
The main topic of the forthcoming Columns 20 and 21 is how the Japanese wrote history, including during and after World War II. Of course, the main target is Kisshomaru Ueshiba. However, Mr Ikezuki has written two books about Sokaku Takeda and has a lengthy blog site...