Inter-Site Suggestion for multiple production sites

We have an environment in V11 Patch 8 and need to have MRP trigger inter-site suggestions with multiple sites. The product is manufactured in both sites, but we need suggestions from the warehouses to drive the intersite movements. Here are the sites involved:

  • SITE1 (International WH)
  • SITE2 (Production Site 1)
  • SITE3 (Production Site 2)

We need SITE1 to generate intersite suggestions to pull product from both SITE2 and SITE3, but the planning tab of the product site is limited to only one reorder site. Has anyone found a way to overcome this?