After some debate, and a search of the forum, I decided on a set of Polar Pro filters for my standard Phantom P4.
They were, after all, a Christmas present - and most grateful I was.  
As many of you will know, unscrewing the lens protector from the camera and fitting a screw-on filter is a
delicate and fiddly business. However, following a tense half-hour and the use of a range of expletives, the job
was achieved - and ND4 filter perfectly attached.  Subsequent flight went well and results were pleasing.

Now, this is where the snag presented itself :  Trying to fit the gimbal clamp for the journey home, I discovered thatIt will not fit over the knurled rim of the filter. RATS!!!  Fiddling about with the filters in the field is not really an option.
Solution:  I've carefully hacksawed off the front disc and about 5mm of the circular surround of the gimbal clamp.
Now, it fits and holds the gimbal steady AND provides much-needed support when trying to unscrew and refit
the filters. That's a fiddly job for the most dextrous amongst us.  For a dithery old codger like me it's even trickier.

As for the Polar Pro filters - first indications are positive.

After some debate, and a search of the forum, I decided on a set of Polar Pro filters for my standard Phantom P4.
They were, after all, a Christmas present - and most grateful I was.  
As many of you will know, unscrewing the lens protector from the camera and fitting a screw-on filter is a
delicate and fiddly business. However, following a tense half-hour and the use of a range of expletives, the job
was achieved - and ND4 filter perfectly attached.  Subsequent flight went well and results were pleasing.

Now, this is where the snag presented itself :  Trying to fit the gimbal clamp for the journey home, I discovered thatIt will not fit over the knurled rim of the filter. RATS!!!  Fiddling about with the filters in the field is not really an option.
Solution:  I've carefully hacksawed off the front disc and about 5mm of the circular surround of the gimbal clamp.
Now, it fits and holds the gimbal steady AND provides much-needed support when trying to unscrew and refit
the filters. That's a fiddly job for the most dextrous amongst us.  For a dithery old codger like me it's even trickier.

As for the Polar Pro filters - first indications are positive.