getting soap fault trying to add sales team list to a customer

I'm trying to update a customer record by adding a sales team list using PHPToolkit 2014.1.
As far as I can figure my code is correct.
Can anyone see what I'm doing wrong?
Thanks in advance.
-JP

        $customer = new Customer();
        $employees = array();

        // sales rep
        $employeeRef = new RecordRef();
        $employeeRef->internalId = 73;
        $roleRef = new RecordRef();
        $roleRef->internalId = -2;
        $salesTeam1 = new CustomerSalesTeam();
        $salesTeam1->employee = $employeeRef;
        $salesTeam1->salesRole = $roleRef;
        $salesTeam1->isPrimary = true;
        $employees[] = $salesTeam1;

        // sales eng
        $employeeRef = new RecordRef();
        $employeeRef->internalId = 40;
        $roleRef = new RecordRef();
        $roleRef->internalId = 1;
        $salesTeam2 = new CustomerSalesTeam();
        $salesTeam2->employee = $employeeRef;
        $salesTeam2->salesRole = $roleRef;