A word of caution here. You need to be sure of the type of epoxy you are using and the cure rate it is designed for. The epoxy sand method will work in layers of compatible thickness with the ambient temperature and type of epoxy you are using. Epoxy DOES shrink but at much less of a percentage than polyester. ALL resins are exothermic and will give off heat when curing. The hotter they cure (faster) the more shrinkage will occur. This can be due to the chemical reaction, the application of an outside heat source, or both. Experimentation is the key before you commit to a full out layup.