With the right tools and a little bit of elbow grease, it's possible to reduce the size of your Quick Wick's clamp by cutting the belt of the clamp shorter.
This is a great solution for Quick Wicks with larger clamps that wish to be used on thinner tubes. Of course, one can always tighten a larger clamp onto a smaller tube without trimming it, but the "tail" of the clamp's belt will protrude and get in the way. Some people choose to just tape down the tail so it doesn't scratch them or catch on their clothing.
If you wish to permanently reduce the size of your Quick Wick's clamp, here's how:
Determine how much of the belt you wish to cut off by tightening the clamp down onto to the desired tube. With a Sharpie or similar marker, make a mark next to the slot that you wish you cut. It should be right under the head of the screw.
With large wire cutters or tin snips, cut the thin bit of metal on either side of the marked slot.
The cut belt will now need to be filed or ground smooth. A Dremel with a grinding (stone) bit is a good option, but a regular hand file will work too with some patience. Giving the cut edges a nice rounded finish will make it easier to insert the belt into the screw housing.