I forgot to mention another trick. Pick up a couple belts for a belt sander. Your choice of grits. I cut them across the seam and this gives me a long, depending on the length belt you select, and stiff belt. I use some double sided tape and tape the belt to a piece of board. You can easilly get a 24" long x 3" belt that is exactly flat when taped down (use sticky paws from the pet shop)

You can also cut short lengths from the belt and it gives you a stiff, but slightly flexable sanding pad, Great for sanding turtle decks and such. simply squeeze the belt by the edges and bow it slightly.

If you want finer grits, check with a lapidary or Rock Shop store. They have, or can get, belts from around 100 grit down to 600 for ultra fine work. These are usually sillicon carbide belts the are used wet. Not much good for shaping balsa, but great for finishing off the fiberglass wheel pants and cowls.

Don