After looking for an appropriate Makiwara striking bag and then ordering one from overseas, I was very disappointed in its performance. It tore at the seams and the eyelets used to hold it up on the hooks after less than 30 minutes of use! I had it repaired twice to no avail!
After seeking out a durable fabric (Danier 450) and someone to sew this bag up, we now have a terrific Makiwara strike bag that is double reinforced sewn and has zippered access opening at the back to facilitate sand (or whatever material you may use.)
It holds up extremely well! Check out these videos of the bag in use:
Some still images: