Just picked up a nice set of PolarPro filters on eBay (thanks, @PingSpike!) but have discovered they are an older version of the Cinema series. They have ridges around the bezel whereas current versions are smooth. According to PolarPro they changed the design after some early reports of gimbal calibration interference but claim this only happened in a few cases.
Does anyone have the older version (with ridges) and have you encountered any problems with them? It would be useful to know before I start mounting them on my Mavic.