Well it doesn't require two light maces, it requires a light mace in each or in both hands (forget which, I'm away from my books at the moment). In any case, a bone-headed literal reading notices that all available hands are full of great crossbow, and activates the feat.
In this particular game we were allowed to go pretty crazy because it was to be the last 3.5 game played before switching to 4E.
The DM gave me some additional leniency because of the intent and function of the character build. This was a character whose only significant contribution was "hit the thing with the other thing", in a party with a Druid and a Wizard. I am a very experienced player, the two players with Big Three characters were not. While there
was some showing off going on, the point was to be strong enough to pull my own weight (and if necessary, save their asses) no matter how deep the trouble we got into, while also being so one-dimensional that I wouldn't bleed over into their niches, step on their toes and make them feel bad. I prefer melee combatants when I'm playing a Big Stupid Fighter, but in this case I chose a ranged attacker so that I could still contribute very effectively against distant and/or airborne enemies.
I included an easy Off switch for the DM in case he felt things were getting out of hand. While I could have optimized around cover, concealment, incorporeality, and other such impediments, I chose not to. Despite his insane firepower, something as simple as a boulder to hide behind or a
wind wall spell stops him cold.
Besides which, it's very simple to do something like 24 attacks per round.
I quit trying to count the time the character surpassed 40 bolts in a surprise round standard action. The enemy certainly was surprised.
Have you considered trying to kill the entire world's population in a standard action?
Being below the curve of the horizon counts as full cover.