You can use figures based for GWSH interchangeably with Square Bashing, as they are both 1 base = 1 company games. Yes, the bases are 30×30, but as with all element based games, the number of figures on each base is irrelevant. You could put 200 2mm figs on each base for a true 1:1 scale game, but it wouldn’t make any difference to the game play. You can comfortably fit three and even four 15mm figures on a 30×30.
I’ve run convention games with both SB and GWSH, SB is a bit more abstract and some players hate it (and it uses a grid).
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke