Dekker is mistaken about how the roller works. It does not force the needle forward. There is a spring that does that. The roller just restrains it. There is play in the internal coupling, and the adjuster travel is limited. But, his procedure is still a good idea. One way to damage the nozzle on an airbrush is to pull back the trigger and release it so it slams the needle forward. Setting the roller the way he does might prevent that damage by limiting needle travel.