Fire Rules for Mounted Targets

[Raellus]

The players in my PbP have just ambushed a group of men mounted on horseback and we need your help.

I can't find any rules (I'm using v2.2) dealing specifically with resolving fire combat against horse-mounted targets.

I'm trying to figure out how to roll for hits on the horses. If I roll a hit on the player's intended target, I'm assuming the rider is hit and I use the human hit location chart. For a miss, how do I fairly and realistically determine if the horse is hit instead? The beaten zone rules won't work because the horse is under the target, not behind him. I also have one player who is not necessarily trying to miss the horses. He's cut loose with a long burst of GPMG fire roughly between the riders' knees and heads. This puts quite a bit of horse in the target box as well. Engagement range is 100-150m and several of the PCs are firing from second story windows. Others are prone on the ground.

With explosive weapons, I assume that if the horse is in the burst radius, I should roll shrapnel hits and blast damage as I would for humans.

Did I miss something? How should I handle this. I just assumed there was a rule dealing with this and now the firefight is on and I'm not sure what the best way is to handle it.