I've been doing 1+100 for an hour with one agitation at 30 mins and getting lovely sharp negs with HP5. Anyone going more extreme — 1+200, longer times? Curious what it does to the grain.
One addition to the 1+100 hour club: give it three gentle inversions at the 30-minute mark. Cured the bromide drag streaks I was getting next to the sprocket holes on brick walls and skies.