Thanks, they suggest 3 unit sizes based on frontage. 40mm, 80mm and 120mm, all of which operate exactly the same with just the unit of measurement (the DU) adjusted to represent half base width.
With bigger forces and a bigger table, I see no game breaking problem with scaling up a bit. Things need to be in command, so you would just need to ensure there are enough leaders to provide enough command radius.
Playing time might become an issue. I think S&S is aimed at the relatively small game, say 8 to 15 units per side and they say that this gives a game of three hours or just under. Going higher and managing the extra units and systems such as opposed dice rolls would add a time factor.
The other thing is that too many dice in the draw bag might give too many chances (or rather better chances) of getting scores of 5's and 6's (very useful scores) and concentrating them in decisive parts of the battlefield, almost ensuring you can get things done there, while I feel the strength of the system is one of no such certainty. So I would say push it a bit, but not a lot.