Non-customer structuring encashment of $9,000 checks received for services rendered. Based on check issue dates, customer may have assisted activity. Any recommendations on how to best address our suspicions with customer?

Why do you need to or why would you want to address your suspicions with the customer. File your SAR and move on. They have engaged in an activity that has no legitimate business explanation regardless of what story they weave.

You could provide your customer with the FinCEN CTR pamphlet, in addition to the SAR as Randy indicated.