if you are concerned about contact thickness of a dip film - you can always remove just those areas (easy enough) and it will not affect your bedding tolerances and or/compression of the film... Interesting observation about hydro-dipping - I paid a reputable/experienced outfit here in WI to do a pair of CCW Glock 26 (plus magazines) as my wife and I had identical weapons... her pattern is still holding strong, while mine I had stripped about a year later due to wear and flaking (I practice with mine quite a bit, so it was not unexpected), with that said, - my original dipped magazine +2 extensions are STILL looking as these were just dipped recently.
in short - it is type of a product which will last a good while and is fairly resistant to common gun cleaners and lubricants.