xbox, you might want to not have singular ones if your stacking them horizontally, you might want a model of a stack of them for performance reasons, plus shadows can be baked into the skin then.

Edit: heres a quick skinless example:



this is a level i was designing a while back, but the sandbag walls were all one model a piece allowing me to not have too many ent's on screen at once and the inner lighting on the walls would look nicer.

heres a quick model Im thinking of putting in a model pack i've been working on, I might put it as a single on gamebeep as well, not sure, but it shows what im talking about: