After completing the installation I have a few parts left over, is that right?
Yes, that is quite possible. We supply a number of extra inserts with the system so that it can be used with different carriers. As you can see in the instructions there are 6 x 2 different inserts for luggage carrier tubing in different diameters. Make sure the right inserts fit onto the outer luggage carrier tubes.
The inserts are slightly longer on the back. Click on the inserts into place with the long back against the bag. See drawing 3 in the instructions. The rail underneath the bag must be hooked onto the disc at the same time. We would suggest that you keep the left-over parts in case you ever buy a different bicycle.