Thanks mstone,
Looking at the discreet thicknesses: 0.4, 0.8, 1.6, 2.4, 3.2, 4.7, 6.4, All of these (save 4.7) are divisible by 0.4, so a greedy algorythm may work just fine.
Comment on Re^2: Finding the simplest combination of descrete thicknesses that sums nearest to the target thickness.