Finer granularity clicking in Scrub Bar

When I click on the progress (scrub/seek) bar with the mouse, the cursor snaps to the nearest x seconds (say, nearest 15th second). I'd like to reduce it so that the granularity that the scrub bar cursor snaps to is about 0.5 seconds.

I've tried adjusting step and seek increments in advancedsettings.xml, and that works fine for fast-forwarding or rewinding, but seems to have no effect on the increments snapped to when clicking directly with the mouse. But perhaps I'm doing something wrong.

Any help much appreciated

(I'm using Transparency.)