Hello Doug,
As far as I know, there is no option field to specify the work default value.
You can create a workflow to do this (On Workitem creation, define Work to the value you want). Unfortunately, there is a conflict if you use DataLoader to create workitem, as the workflow will override the values you try to import.
If your WorkPolicy is set to "Fixed Duration", the Work will change when you change the task duration, so maybe you want to define the default value of duration instead?