I am trying to convert color negatives into positives and struggling with removing the orange mask and getting usable colour after inverting.

It seems that I constantly clip the red channel no matter what I do, please can some of you take a look at my set up and offer some advice?

**Here's my current workflow / setup -**

* Nikon D810 - 100mm Tokina Macro - Copy stand - LED Lightpad (artograph A920)- Negatives held in old carrier from enlarger - I use a custom WB of 2900K.
* I then 'scan' as Raw files, put in Adobe Lightroom > set the camera profile to 'camera flat' take off sharpening etc. then open in Photoshop.
* In Photoshop

1. I Open two files - one is the image I'm going to correct, and one is a blank film leader taken from the same role and exposure (I use this for the WB).
2. I open a levels adjustment layer and using the grey dropper I select the blank film leader and this helps to correct some of the orange mask. I then invert and use auto level curves layer. Finally I tweak the colours to try and remove colour casts (this has varying levels of success). The full steps can be found on this blog <http://mfphotography.ca/blog/2015/3/23/colour-film-scanning-revisited-part-2> and in the youtube video that Mike made - <https://www.youtube.com/watch?v=bVxtIqmEnTk>

**Questions / Things I have noticed with my technique** -

1. When scanning the negative, I have to underexpose the image quite significantly to avoid clipping the RED highlights in the histogram of my Nikon D810. How do I get a good exposure without clipping the red? I am guess that when I clip the red it makes it harder to get good inversions in Photoshop. Maybe I could use a filter? Any idea which screw in filter would work?
2. The negs that for some reason don't clip the red channel as badly, seem to convert better. For e.g. I have an old roll of Kodak Portra 400 at home from when I used to shoot film a few years back, that seemed to scan much better than a recent Fuji 400proh that I converted. The Fuji neg mask seemed more dense, perhaps this is bad processing at the lab that was affecting my results?
3. I have tried the trial version of colorperfect and the results of this don't seem to be as good as the Photoshop method, they also seem to vary wildly with each negative that I open.
4. I am working sRGB on camera, in Lightroom and in PS - is this recommended?
5. Has anyone tried this approach.
6. Sometimes I get best results from using the white balance tool in Lightroom before opening in PS and doing the inversion.

Finally I would just like to say that so far I have got good results from DSLR scanning in terms of quality of image / sharpness, but I am really disappointed in the colour aspect - I am almost thinking of trying a scanner like the Epson v700 instead. There must be a way around it however - I hope at least!