This question is the second part of my previous question about piezoelectric plants. In summary: The plants on my world generate electricity from kinetic energy (piezoelectricity) instead of or paired with photosynthesis. The plants are hollow to resonate vibrations and absorb more energy this way. They grow in areas with frequent tectonic activity or with sufficient wind or rain. There are many variants of plant each specialising in one or more energy sources. In this question I'll be asking about rainfall as their power source. Also for the sake of the question just assume the biological process works.
As we all know, plants grow in the direction they are getting light and nutrients from and are also optimised to grow shapes that absorb efficiently. Leaves are wide and flattened to collect sunlight and exchange gases easily. Branches are fractal and grow in the golden angle, this angle promotes adequate ventilation of the plants and is the optimal arrangement for light absorbance. Tree trunks are solid and roots are also fractal to absorb as many nutrients as possible and keep the plant firmly attached to the ground.
How would these plants be shaped to get the most energy from rainfall?