I don't imagine you would need more than 500 casts of Ice Barrage, depends on world pop of course. IIRC cannon decays after around 25 minutes. Just replace it to restart the decay process. I would bring something along the lines of 3 Brew, 2 Rest, 3 Brew, 3 Rest, repeating. If you don't plan on safespotting, but freezing, there is still opportunity for error, and it leaves you vulnerable to Supreme as well, if you're more towards the middle of the room. If you're planning on running out of Supremes range, then you would probably be safespotting Rex to begin with. If you've got your cannon going, I imagine broad bolts would be fine, and save you a fair bit of cash. If money isn't a concern, I would be using diamonds as it were. Elsewise I would cut out a brew and bring an additional overload. Looks fine after that. OH AND, I HIGHLY suggest using an EE / Elite EE. It helps time when you should redose with your overload, and it can save you some food. Nothing worse than brewing to 1150 and then noticing your overload JUST wore off.