the trick is to shorten the tube and turning to a 1.882 inch length -- see the Az Sil page for the click pen for pictures. I had a couple of stabalized spalted Sierra pens that had small chips at the ends. Trimmed them down to 1.88 inches and assembled with the parker refill -- worked well.
Note that the long click pen is set up for a uniball refill -- or a pilot G2 refill is the same length. The Uniball or Pilot provide a nice gel writer pen with this solid feeling click style pen.
I have a couple sets glued up with long click gel writer, click pencil, and shortened parker click ball point pens - They step down in length nicely and provide a 3 pen theme with three different writing styles. Visually, you can pick the pen based on length for the style and feel you are seeking on a particular day.