I’ve released a small AR calculation bugfix this afternoon. Turns out that bows always get the two handing strength bonus when their AR is calculated. It makes sense, but not something you would intuitively know.
Also keep in mind that your in game displayed AR for a bow takes into account the arrow type you have equipped. For now, Mugenmonkey does not support that feature – so the AR you see would be what the game would display if you had no arrows equipped.