1.5 months post lipo and I have a problem with my buttocks/thighs: lots of fat removed and hollows.

Dear, based on your photos, it seems that the amount of sagging skin on banana rolls are only manageable by direct excisions. Also to improve your buttocks shape, I recommend to increase its volume associating with any available fat to turn it more natural. 

The appearance of your banana roll is common after fat is liposuctioned from that area. The banana roll acts like a supportive bra to the buttocks, so when it is removed, everything tends to sag. You now have excess skin creating rolls in that area. 

HD Vaser Liposuction technology is the only viable option to optimize contouring of your highlighted area. Using Vaser technology ensures a smooth spread of the fat transfer. Also, vaser technology allows us to harvest up to 40% more fat compared to traditional methods which allows us plenty of volume for the butt revision. A Skype consultation with a vaser liposuction specialist can assist you in definitive recommendations.