This is naturally depending on the height of your resonance box. If the resonance box is similar to the one described above, two concert piano stools mounted to their highest position are ideal to support the box. These are also quite easy to find in any concert hall and save space in your car. Make sure the set-up is not mounted too high, because of playing convenience. If it’s too high, you tend to constantly overplay your muscles and it will be hard to make it through the piece. If it’s mounted too low, back problems will occur soon.
When practising and performing the piece, you will notice that what is written for the voice in the score, needs to be performed quite independently from what you are playing in the hands at that moment. This needs quite a lot of attention to obtain a natural-sounding result. I practiced these passages extremely slowly, at 1/4th of the original tempo. Then, I sped up little by little, always making sure the result sounded very natural. If the basis for this is constructed in a natural way, the end result will sound flowing and easy.