My Christmas game used Simplicity in practice by Neil Thomas on a 2'x2' mat. Rules mostly as written and two Wofun bases per unit (6 cm wide). A new houserule I used is that if a unit is firing uphill, the target gets to save as if in cover. I got this modifier from an old ACW ruleset called Whipping Bobby Lee (1990), and I think it makes sense given the ballistics of musket and cannon fire. It also encourages taking positions on heights. Nevertheless, it is uncommon to find this modifier in rulesets.