I didn't see that the paper mentioned was a matte paper, but I did take a look at some measurements of my ink separation images with gloss papers and the densities you posted above are close to what I am getting. (Canson Platine maxes out at 2.9 at 90% and then falls back down to 2.8 at 100%).
Be careful setting a boost up to 90-100 because matte papers tend to lose density when they are flooded with ink.
I took a look at a few other papers I've measured and profiled. These are all the OEM Matte Black channel with the ink limit set to 100%, and are meant to just give you some idea about what you should expect with the P800 and matte papers.
Moab Entrada Natural and Bright White go up to 1.59 at 50%, then max out at ~1.64 at 65% and then fall back down to ~1.60 at 100%.
Premier Art Smooth hits 1.68 @ 50%, maxes out to 1.71 @ 65% and falls off to 1.68 @ 100%.
Canson Edition Etching does a little better. It hits 1.66 at 50%, 1.71 @ 65%, and maxes out to 1.74 @ 85% and then doesn't fall off as it reaches 100%.
If you are going to get into this you might consider finding a used i1 Pro 1 for profiling. I just got a SpyderPrint measurement device to format my profiling tools and workflow for it, and it doesn't perform as well or make the process as easy as the i1. I taught a private QTR workshop yesterday and they had an i1 Pro 2, and, in some ways, was not as nice to use as the older version.
Hope that helps,
Richard Boutwell
http://www.richardboutwell.com/