Sizes

General Rule
Each size has advantages and disadvantages

Small

 * Can move through (but not finish on) half-tiles.
 * Obstacles as if barriers (both ways)
 * LoS must reach center of square tile (dot) (both ways)

Medium

 * No impact

Large

 * Cannot gain cover.
 * Counts obstacles as if difficult terrains
 * Melee reach is always 2 tiles.

Ideas not used or developed

 * Impact on Carry weight ?
 * Number of carriable items
 * Pros/Cons for medium.