Harrim is consistently depicted as wielding a flail and shield, which makes perfect sense for him. Except for one problem: Groetus's favored weapon is the war flail, not the common flail. Harrim isn't proficient in flail until 3rd level, and never really gets good with it. But he's really, obviously supposed to hang onto his shield, which he can't do with a war flail.
If I need to make a PC-style build for Harrim (which, I might), would it be unreasonable to just rule that Harrim follows a slightly more dwarfy heresy of Groetus, that favors his flail-and-shield style instead of the larger war flail? I don't have any PCs that might decide to follow Harrim in his faith of despair (or really, any religious PCs at all!), so I don't have to worry much about them asking for other heretical cults with game-mechanical benefits. The other solution would be to downgrade him to mace and shield, which seems kind of lame.
