We play the rules pretty straight, except for two changes which help with armies incluiding cavalry. We find that light horse aren't a great troop type in the rules. This is partly because they aren't much good in melee, and run huge distances when they get a flag (often perishing when they reach a table edge).
Firstly, we use a slighly deeper table than the boardgame. Our Hotz mats have two more rows of hexes than the standard C&C boards, and this extra depth is very useful when armies with cavalry, giving them a bit more space to manouvre (and to run away!). Frankly, if we had 3 or 4 more rows of hexes, I wouldn't be unhappy! But my table depth is 48" and there is no space for them.
Secondly, we have amended the evade rules. In the standard rules, when evading, the attacker rolls a number of dice against the evader depending on his troop type; paradoxically this means that the slower troops, eg Heavy Infantry, with 5 dice, are likely to inflict more casualties on evaders than faster troops such as Medium Cavalry with 3. Moreover, the potential casualties inflicted on evaders seem disproportionate by comparison with the one or two dice that skirmishers inflict through shooting.
Soooo... the Muswell Hill Amendment is that when skirmishers evade, they take one dice when the attacking troops are slower than them; two if the attackers move at the same speed, and three if the attackers are a faster troop type. Simple... but it makes a huge difference with battles involving light horse, such as Ruspina.
Here are some Scythian light horse I prepared rather earlier.
We played the Ruspina scenario again last night, with 14 units of light horse, and it worked very well. I must say that I now feel that Carrhae could just about be squeezed onto our table. If only I had 80 or so horse archers, rather than two dozen...