[Bibio]

 That only works if your display doesn't activate its own tone mapping. This won't work for everyone. Mostly, the gamma can be changed and maybe some of the values will be further compressed. I am betting this only works with a few displays. They are pretty dumb when it comes to tone mapping, even when madVR changes the metadata to say that it has been compressed already. The display may not interpret this metadata correctly.

There is no nits value in the profile logic. Although, I don't quite understand what you are trying to do.   

 i use madVR with FULL Group Profiles and Profiles within the groups. this gives me pretty much full control within madVR for each video content type.

there are only two types of content that give me headaches, the first being HDR 4K due to the nits values and very old DVD's that are very poor quality dating back to pretty much when DVD first came out.

if i could set different profiles that were dependant on media PQ then it would make life a lot easier and this is what i'm trying to achieve.

a little question that i'm also confused about. with me being in the UK are all my DVD's classed as PAL?   

And, yes, I would assume all of your DVDs are PAL in the UK. They should be 25 fps rather than 23.976 fps. 

 that would be 25hz to 50hz though would it not or am i thinking about TV broadcast interlaced?

just like NTFS is 60hz so their DVD format is 30hz?