Like I keep saying, you should be very reluctant to work with subcontractors when planning a hit. The security and reliability risks are just too high.

At a minimum, you need to retain and exercise the right to vet any sub-subcontractors for quality-control purposes, and frankly I would suggest that you not allow a subcontractor to hire sub-subcontractors at all. If you do, you need to make clear that they need to make clear to any sub-subcontractor that they are not to hire sub-sub-subcontractors, much less allow any sub-sub-subcontractor to hire a sub-sub-sub-subcontractor. I promise you, the sub-sub-sub-subcontractor will screw it up 99.99% of the time.