If you can afford it, you can also give the FM55 a try.
I have another model, FM34, which uses the same type of mechanism for securing itself to the head of the light. Apart from the size, it's pretty much the same.
I can only say that it's an over-engineered and over-built monstrosity. It will absoposilutely NOT separate unless you disengage the grip.
Apart from being built like a tank, another positive aspect will be that it's a flip-on filter, so you can just flip off the cover to get natural light, instead of putting the entire unit on and off.