It probably wont work. You cant avoid shifting weight. Dont worry about the scale. Do what you know you need to do and gueage your results by the mirror until you can make one scale work.
What s the maximum weight that the scale can weigh? If you weigh more than the scale can handle then it will show you an error.The most accurate way to weigh yourself is with a scale that is calibrated using known weights on a monthly basis. Even if you weigh yourself using two scales but neither one is accurate, then it defeats the purpose.
I suppose it could work, as long as you have equal weight on both scales.Dont put more pressure on one side than the other.