Request backup bus # increase.

[mariokiller64]

Is there anyway to increase the number of backup that comes when I call in, say zombies?
I've tried something like this

        <Human>
          <Character>npc_Gat_zombie</Character>
        </Human>
        <Human>
          <Character>npc_Gat_zombie</Character>
        </Human>
        <Human>
          <Character>npc_Gat_zombie</Character>
        </Human>

but seeing as I just started modding today...I'm not very good at this stuff. Basically, I couldn't call anyone without crashing and my zombie calls disappeared lol.