You brought up an important point. You have overexposed to fight contrast. Well, if you overexpose and either under develop to get lower contrast or develop normally, you will be talking about at least 2 stops which is about ISO 6 or thereabouts. This will reduce the contrast nicely, but it will not center a tonal scale at normal development.
All of my photos include the MacBeth Checker and have the neutral scale centered with Dmin on one side and Dmax on the other, and they were given normal development, no under or over, and no flash.
I think that all of this is important. I am trying to get at the full tonal range. To actually do this with a paper, I suggest a grade 0 or grade 1 graded paper.
As for spectral sensitivity, the Ilford MGIV and most graded papers today have a short green sensitizer that is much shorter than I expected. It peaks at about 520 nm as opposed to 560 - 580 for a "normal" green sensitizer. This gives things much more than blue or dark green no detail or image at all and seems to further increase contrast demanding more overexposure to the eye.
Take a look at my images above and see what I mean about centering the density values on the scale.