Effect of mass, is a non event, on combat, for it to have an influence the unit with greater mass must move the lower mass unit so as to allow more men in contact, watch elephants(48 vs 24) fight in custom battles to see the process of pushing apart the formation, allowing doublleling up against a target by the numericaly larger formation with greater mass, to allow the frontage a model formation tells it it must have, to fight against another, allows that greater mass units can push apart or into others to allow more in contact and hence in the combat, since infantry .7 frontage greater mass units pushing into 1 or 1.6 less mass units brings almost no extra men into contact, the mass incresae meerly alows them to occupy space, but certainly no bounus for men in contact and thus increae in combat effectivness by allowing more men to be in contact. Mass has no effect on combat, so costing it as an effect on the combat element of a units cost is unwise. Should mass be part of the units overall cost?, perhaps, but so small a part as to be almost not worth the effort, the space it wins is to all and intents and purposes unsuable on the battlefield by other units as the engegement outcome is determined before the space won due to push back can be utilsed. However should combats in general take longer to resolve, then mass would push formations around and play an increased part in shapeing the outcome of the engement not meerly the location of the outcome on the battlefield. Large formation being pushed back by smaller more mass formations that are not eliminated by casualties at the present rate, would win ground for others to use, so the interplay of unit sizes becomes more important, a Roman unit/third the numerical size of a Celt would push it back during combat resolution, the celt would have many ranks and absorb the loss and yield ground, the Roman from his 4 ranks removes his losses from unengaged rear ranks, and moves forward to occupy/win space, but if the ratio of attack/defence was altered, ie average foot or mounted attack value was not what is is but was lower, or defence was higher, thus making casualties less frequent, then mass would shape the location of the outcome, because other units would use the space freed up to deploy and influence outomes elshwere, in that 3 large units charge in and the Roman push back the centre one, hold in place on the two flanks, which frees up space in the centre after a short time for a second line unit to wheel and come in on the inner flank of the two pinned in place attacking units.