Using EAI to 'Associate' existing Contact to a new Parent record

I think I may be going a bit bonkers, as I thought I had EAI sussed!

I have two Data Maps and two invocations of the Siebel EAI Adapter. The first part of the process creates an Account and a Contact. The second part of the process attempts create a new Service Request and associate the Contact from process one to the SR.

I have two IOs with corresponding BOs:

Account

|_ Contact

Service Request

|_ Contact

Both 'Contact' ICs have a 'Person UId' User Key defined and configured as the sole User Key in the IC. When I create the Contact in process one, I set the 'Person UId' to something absolutely unique in the system.