I could see the weave pattern in a pure black job, the first imperfection I had noticed. I was also dissatisfied with the opacity of the print. I rectified it by cranking it up to 16p 1440x1440 to dump a ton of ink on it. It took forever and gassed up the office, so I will look into some other tweaks next time. There is a setting to treat b&w images as CMYK (instead of default RGB) and I may try cranking up ink limiting a bit or maybe converting the b&w to CMYK and specifying values.
This was on 3M 7725, for which there was no profile, so I used the 180-10 (old ones).