Didn't feel an difference
In preparation for my son's wedding and wanting to wear 3" heels since he's 1 ft taller than me, I tried Vivian Lou inserts. I put one insert in one heel and didn't put the other in the remaining heel. I then wore the heels around my house for about 4 hours. I didn't feel any difference between the heels and I did notice that my foot did slip forward and I didn't notice the insert shifted my weight to my heel.