Well, you are free to do as you wish, but I'm not interested in trying to support additional databases for the WebStore until I feel that the schema has stabilized. Its a lot of work managing upgrades and schema changes. Currently this feature is not very mature and there will be major schema changes to come that I don't want to have to support for more databases.
In fact I think I need to remove the WebStore.Data.pgsql project from the solution since it is only a stubb and it leads you to try it.
I no longer use stored procs for implementing pgsql data layer either because its also too much work to maintain. I have no table scripts or anything for you for pgsql and webstore. When I get to the point where I am happy with the schema, then I will implement pgsql and it wil not take me long to do it, but until then it will only add to my workload and slow down progress.
So, if you try to implement it yourself, you will be chasing a moving target.
Best,
Joe