Ed, for these sorts of images you may be better off using some of the newer f-type papers -- Moab has some in the Colorado Fiber line, and there are others from Crane, Hahnemuehle, and Innova, too. There are some versions of these papers that have a fairly low gloss (little sheen) and therefore come reasonably close to resembling a matte finish. You'll end up getting lots more shadow detail (and deeper blacks and a wider gamut in the shadows, another plus).
It is also possible the custom profile that you have for the Entrada is just not providing sufficient shadow detail. Depending on the software package used to build the profile, the number of patches in the target, and the software options chosen, there are cases in which shadows will be compressed. Do you happen to know which profile software was used to build your custom profile?
Have you tried the Perceptual rendering intent?