Here are full-resolution crops of HP5+ shot and developed identically in XTOL and the concentrate. XTOL is on the left; concentrate on the right.
XTOL: hp5-xtol-crop.jpg Concentrate: hp5-conc-crop.jpg

The scanner is a Nikon Coolscan IV-ED, which has a resolution of 2900 DPI on the negative.
What do you think of the grain and sharpness?

Also, I attached a down-scaled scan of the entire frame.

@Kirk: Push-developing is a good idea; I'll do that. I'll also do it diluted 1+1 to put even more stress on the developers.

Mark Overton