I wanted to play with the takadai before using the weird cotton/PU yarn supplied. So I used 2 strands of 10/2 cotton per tama to do a test warp.
I have a big collection of swords as a backstrap weaver. The one I am using is 18″ long. The tip is pointy enough to “pick” really easily and narrow enough to work well. Sometimes the sword is not laying flat, with the end closer to me raising up a bit. It seems like there is a sweet spot. It will do it when the the weaving is too close to the torii, then again when the warp threads are too far back away from the torii.