I made a quick little video describing the problem I have with my new YN-300 LED lights:
The knob is twisted on as tight as it'll go. This may just be a "you get what you paid for" kinda problem... but these lights definitely weren't the cheapest lights in the world. Any help or tips would be appreciated.
The design of the mounting system is flawed.
What I'd suggest you do is remove the part held on by 4 screws that has the two fingers. The get someone to make up a piece of say 3mm Aluminium with a 1/4" threaded inset. Then you can use any number of ways to mount the light onto stands etc.
I've looked at quite a number of similar lights and avoided them because they have the same design flaw that leaves the user at the mercy of their weak friction clutch. By comparison the Z96 comes with a 1/4" brass insert and a pretty weak mounting system but the user can throw the weak part away and used anything with a 1/4" thread on it. Much better arrangement.
One thing you could try if the above is all too much trouble is to put a piece of card or paper between the fingers / leafs of the friction clutch or even try roughing up the plastic with some coarse sandpaper.