I designed this to put my Suito Elite Smart Trainer on tennis balls. This allows for significantly more side-to-side movement and also reduces noise/vibration induced into the floor.

I use 4x for my suito. The feet are mounted using 7,5 mm cable ties. I printed mine using PETG at 100% infill. 

I added the Fusion360 model. Note that this has been thrown together by a CAD dilettante (me) and does not follow any sound design-principles. Good luck! 

!!! USE AT YOUR OWN RISK !!!

I designed these for my use-case. If you are a 100kg sprintcoloss that puts out 2kW, consider not using these. I'll take no responsibility for you crashing indoors!

Take care!