Not as fun, but less expensive that tatami mats for test cutting. Will cut with a clean line with a sharp or even a decent cut with a blunt sword. Then you can trace the cut for feedback on your form. At 1200' long, there is plenty of cutting for the price. And you can put it in the recycle bin when done.
It can be freely hung from a roof with rope. Some friction is best to keep it from free rolling.
I'll have some new suggestions and ideas as time goes on.