My battlefield works out at about 1/3the size of the standard Impetus battlefield. The standard frontage is 12cm per unit. So I am looking at at four cm unit width. Seems a bit big for this battle.
The Basic Impetus armies are 7 to 10 units, the guide to the Battle I am using has maybe 12 units on the Regents side, and the Queen’s Army is larger, but I’d represent that by having some of the pikemen starting in larger blocks.
I think the next step is to cut some paper counters the right size, see how that looks on the field. If the army is too wide then I may reduce the number of units