The way to minimize the instability issue is to use well quartered wood. If you have to make a 4-piece back then do it: it won't hurt the sound and will make it less likely to warp or crack. Apple is fairly soft and low in density, much like soft maple, and bends nicely. Often with older wood you can get some nice figure, and it's easy to finish. Expect a tone that is more 'maple' than 'rosewood' and you won't be disappointed.