Alumicraft Street Rod Grilles, which offers inserts for a number of kits and rods, now also has aluminum sanding blocks.  Unlike high-density foam blocks, these blocks don't flex or warp with water or heat, so they stay flat when sanding a flat panel.  The GoToBlocks are machined from 3/8-inch aluminum plate and the ergonomic handles are bolted on to keep them perfectly flat. They are designed to use the 3M-style StikIt adhesive backed paper. The five-piece set includes a 22-inch long beam board, an 11-inch long round handle board, an 8-inch long flat block. These 3 blocks all have a rounded edge on the sanding surface, so you don't have to worry about digging into the panel.  Also included are two smaller 1 x 6-inch detail blocks that can be cut or shaped for custom applications. The set retails for $195.