You have also helped me design my own grappling dummy. I had a previous grappling dummy that fell apart and then I had wanted to get one like you had but I did't have the money so I designed one that's not heavy but as a result allows me to focus on speed just as you said on the kettlebell thread.
My new grappling dummy is made from an old boxing bag with a heavy medicine ball as the base, stuffing for the rest and a judo gi jacket on it wrapped up in bungee chords. It's works wonderfully, I can focus on speed and besides I've found when throws I prefer (usually sweeps) are done right the opponent doesn't feel heavy anyway. (Maybe next year I'll get a dummy like yours.)
How is Mr Wang's grappling dummy made? I am asking this for a friend who may be interested in a cheap, homemade dummy.