Yes, you're right. I did it few days ago and the result was very good with almost perfect grays.
Better then Curves+matrix.I've just noticed that the XYZ profile was made with Argyll 1.3.2 and the Lab with 1.1.0.
Does it matter? This is from XYZ
Thanks a lot Andrzej
Try an Lab cLUT profile. XYZ profiles may need more smoothing than the default. It would help to send me the .ti3 file so that I can see what the profile looks like. Graeme Gill.