I understand what you mean by xbow takes 2 slots because 2 of the bows I use takes 2 slots as well. However there's a few options to choose from for a 0 slot weapon, which means 2 slot heavy xbow or an arbalest + 2 steel bolts should be 4 slots and an empty slot with a 0 slot weapon such as pickaxe or hand axe or hammer. Now on a battle server you don't need 24 bolts most of the time because more often then not you will die before even using half of those. I know as an archer I have (depending on the the arrows i'm using) either 40 tartars or 34 bodkins which I very rarely go through in 1 round. If I do I pick up random arrows on the ground. Now usually ranged fight against ranged in battle or siege servers and in my +2 byrnja I often get 1 shotted by arbalests so you clearly don't need that many bolts. But back to the problem, if you are last alive as ranged you just gotta try to block and try to make them hit each other. It's the only way