Cheryl, just try to get the short ones the same length, and the long ones the same length. Blocking them will help. Don't worry about the width (which WILL change if you block them). The floaters will make everything work just fine and Sue's directions tell us how to figure the right size for the floaters! I think it's magic!
You might want to check your seam allowances to make sure you are stitching correctly. If you measure your FINISHED squares in the 4-patch blocks, they should measure EXACTLY 1" x 1".
If that measurement is off, do whatever it takes to correct your seam allowance for the rest of the project. You can either move your fabric as you feed it under the presser foot, or you can move your needle to make up the difference, if your machine has that feature. On my Webshots album titled THIS IS A TEST, I show how you can check your seam allowance.
And remember....we are dealing with fabric here, and not tempered steel. Minor adjustments are possible!