When using the original Impossible Table arms, you will notice that as soon as you start putting more weight on it, the arm itself starts to bend. This small bend causes the outside strings to lose more tension, which will then lead to things falling over.

I did a quick design of a stronger arm to combat this. With this, I was able to balance a 2lb weight on it. After that you start to see buckling of the table itself, so more improvements would need to be done there to increase it further. I used a hex design table, so maybe the original would be less flexible.

I used 100% infill, but I am sure they could be printed with way less.