Adding Adv. Project Task Predecessor Sublist Records via Scripts

Hi--

I've built out an engine that allows for template projects in a way that matches our work flow and resource assignment methodology.  Project creation, project task creation, resource assignments, linking to customer/opportunity records and protect task parent/child relationships are all working the way they should. 

However, the last thing I need to get working are predecessor/successor relationships.  The Records Browser for Project Tasks indicates that there are two required fields for the predecessors sublist.  One is the predecessor task and the other is the predecessor type.  The type value is eluding me... and I can't find what it's expecting.  When I pull predecessortype field from search results, for value I get 'Finish-to-Start' and for text I get null.  However, when I try to set the predecessor type to 'Finish-to-Start' I get and invalid reference or key error.  That type field doesn't default and I can't