You will need the
MESH_ju-beos_slimtop050802 mesh for these to show up properly in your game.
Here are another (rather brightly coloured/textured) 8 slashed t-shirts for Marvine's slimmer bodybuilder.
Credit goes to Marvine and Beosboxboy for the mesh, wirelessguy for the textures and Special K for the inspiration.