Unbounded 3d voronoi from spheres

I am trying to create a group of unbounded voronoi cells based on points generated from the centres of spheres (with unique sizes). So far I have not been able to get the cells to align with the spheres (see screenshot). When working with the 3D voronoi component you need to create sacrificial points round the outside to avoid your main cells being constrained by the bounding box that is generated. As a result of these extra points, the voronoi cells get distorted and so do not line up accurately with the original spheres used to generate them.

Anyone have an idea of a better way of doing this?