Eloquintet,
Just a little advice. To be truly accurate, try this approach. Instead of using the difference of the actual length and the target length, use the full length that you need. What you are describing will only lessen the problem that your are trying to fix. Your source measurements are still rounded off, albeit a very small number. Given enough continuous dimensions you will end up with the same problem you started with. The sum of the parts will be different than the whole.