Performed quite well, I think

Looks good. Will it hit anything while starting up?

no, it's well clear during initialisation.  I even used the modified lens hood on this flight which seemed to work quite well

Looks great, I have a set of the MC variety and tried the ND 4 yesterday and it seemed to work well, although the light was flat and grey.  No problems with them on installation/calibration either.

Thanks.  I've got a set of the PolarPro ND/PL filters that I will use just for stills.  Even then, I found that there was variation in the hue of the blue across the width of the sky due to the wide angle of the lens

What was the shutter speed using that ND8 filter?

I am asking as some of the shots are slightly stuttering and maybe a even more reduced shutter speed could have made it smoother.

Shot with 2.7k, 25fps, 50th shutter speed