saw this design and thought it was a good idea, not sure where the original one came from as there were many versions floating around. however when i printed it i realized that there were a few flaws i didnt like so i made some adjustments to the design. Firstly i made the mount plate thicker, the original broke coming off the printer, 2nd i made the ball tension-er item flower-thing more rigid to hold the ball alot more firmly, as in that ball isnt coming out even if you lift or move the printer. you might need water or soapy water to get it in. i did it without water but i would say water might of help me along, either to help with the thirst of the workout i was getting or to make the ball slippery you decide when u get to that point, err dont drink soapy water. Lastly i made it 2 pieces in order to make it height adjustable. It always made sense to me to make any kind of legs adjustable as tables and floors can be skew. i felt that since it was 2 pieces i had to make it fairly tight fitting for structure, less than .5mm of difference, you will need to wear it in with a few dozens twists on and off should do it.
Added long version for anyone who wants to put legs on middle rail of cr-10 and tornado, i didnt but i see some that did so i made it adjustable as well.