Very interesting. I can provide more details off line as I am not priveleged to generally release my methods in detail.
I can say I use a custom made test chart, read with a Spectroliner and interpret with modified software including Profile Maker and Profile Editor. I try to lay as much ink as possible whilst retaining maximum shadow tonal seperation. It may be that this concentration on deep tones has pulled the CMM DMax back. I will definitely look into this further. Further the profiles aim to clarify colours, making them more luminous.
I have quite a bit of experience with HPR , having used it for 2 1/2 years and created around 6 specialised profiles for it. I have only been printing on CMM seriously for couple of months, so am not confident I have extracted it's full potential yet. I would say though, that prints on CMM with the current profile are visually producing some of the most accurate renderings I have seen. B&W using all 8 K3 inks (not Advanced B&W, which clips) is absolutely neutral.