A belt line incision may not give enough access to the upper buttock, where upward pull can also lift the upper part of the back of the thighs. Using an incision below the buttock will allow a lift to the posterior thigh tissues, but this will bypass lifting the buttocks. Most surgeons will want to tighten the buttocks as well as the posterior thigh. For this reason, the under the buttock incision is not the most optimal.
An alternative for your situation may be a gull wing incision, below the belt line incision already in place, but placed just above the curvature of the buttocks. This would allow pull on both the buttocks and posterior thigh. It may not be possible to avoid two scars in the back if the belt line incision is too much above the gull wing incision. The proper choice will depend on a consultation and examination by a Board Certified Plastic Surgeon with experience in lower body lifts. Best of luck in your inquiries.
