It was me who offered advice on how to repair the cups but you need to know a little about plastic modelling techniques. My husband is a professional model maker for museums and collectors. Here's what you need. A product available at model shops is ABS plasticard..it comes in sheets of varying sizes and thicknesses. The thinner sheets are usually 0.15 or 030 thou. It can be cut very easily. Rough up the surface of the dome along the area of the crack with sandpaper, cut a strip wide enough to span the crack...apply glue, which is designed for use with plastic...modellers glue, and press the strip into place and allow to dry. That should seal it 100%.