Some random thoughts:
I find that the printer profiles really aren't the issue with the 4880 or 9880 and B&W printing but the advanced B&W settings, color->B&W conversion and source document profile are the key points.
The only way to really get the best from the printer is a lot of trial and error since there is no way to get a preview on screen that is in any way useful.
Do convert the file to B&W before printing since the printer driver conversion may not be the most pleasing result. As a photoshop hint I usually use more than one conversion layer to get the most contrast out of a print.
Printing with an RGB profile yields a far different result than a gray scale profile but neither one is better than the other in all cases (at least in my experience) so you might want to try both if an image isn't grabbing you. A 20% dot gain GS profile is often very dark.
I keep a small notebook as a log of all the B&W prints that go out with the file name & date, and settings from the B&W driver tab. This is very helpful for both consistency and tweaks.
For what it's worth I start at neutral darker 0 9 9 9 0 and go from there.
Happy printing....
Doug