The rules don’t really cover 2 gun sections (one model gun) such as that deployed in some historical scenarios.
Here’s a scenario specific house rule I've used which seems to work.
One gun model fires as a four-gun (two model guns) battery but fires at half effect. Ignore any references to ‘Elephant Tests’ on the Artillery Fire Casualty Chart. In addition, it is dispersed when only four casualties are received. It may not limber and move once three casualties have been suffered.
Incidentally I also halved the points cost for a two-model gun battery, for those that use them.
Try it out and post any views.