Our tryout player is running a SM+1 Barbarian, and the nebulous rules about what should be and shouldn't be Oversized threw his gear list off a bit.
Here is how I summarize my rulings on this matter:
Oversized, yeah or nay?
- armor and clothing must be.
- shields should be, and we penalize you for too-small shields (basically, a DB penalty)
- tools and weapons can be.
- equipment shouldn't, unless it's also clothing/armor.
Which makes it easy. If you had, say, a SM+1 bow, you'd need SM+1 arrows and a SM+1 quiver for them. But a SM+0 bow? No problem, normal sized stuff is fine.
Backpack? A bigger backpack would hold more. You don't need it to be bigger to use it.
Rations? Nah, one meal is one meal. Presumably you stock up on more calorically-dense foods, that's all.
We've found this set of guidelines really takes care of most issues with "Oversized or not?"