Can a Fat Transfer at the Top of the Bum Help with Sagging from Banana Roll Lipo? (photo)

I'm scheduled for lipo on my knees, anterior thigh and banana roll. To prevent worsened sagging from the banana roll lipo my board-certified surgeon suggested also removing a small amount of fat at the top-outer area of the buttocks (to contour) and then a fat injection at the top of the bum, in effect to "boost" and lift the bum. He likened this to how a balloon props up when it is inflated. Will this work? As FYI I'm 36, 5'6.5", 140 lbs, my BMI is 22.5, and I exercise 3-4 times per week.