C'est vrai que le SK est flou sur pas mal de points
De A2.51 :
« All terrain on an offboard setup map is considered Open Ground except for off-map half-hexes which are butted against a half-hex of some other terrain type and hex rows Y, Q, and I which are road hexes if the board is butted lengthwise. If the board is butted widthwise, all offboard hexes with a coordinate of 5 are considered road hexes. Roads share the same status as the majority of on-board roads of the adjacent board »