This is awesome Geoff! The Explode by Face Side is just what I needed for my Oathsworn: Into the Deepwood modelling.
I am, however, having some weird things happen when I create Merged Pools that use Custom Number dice. I have four custom dice types, each creating a pool of N dice that is then Merged. Strange things seem to happen when I change the value of N between runs - especially if N is set to zero. The model is too complicated to describe here, but Paul Grogan describes the method here at 00:07:10