Actually, mesh=wireframe. The skeleton is something separate that makes elders have bad posture even when they have on adult clothes so they aren't so saggy. Normal/bumpmap is what makes the clothes look bumpy or indented in the game.
Have you checked out this tutorial on nudes:
http://www.insimadult.net/showthread.php?t=26227 It's by BeosBoxBoy, the master of nekkid Sims!