Bummer, I was SO hot today, it is in and out of the 90's today and I am thinking: I hope that vest is working for 'the Blaster...
Maybe if you filled the reservoir 20-30% and froze that into a block the cold would last longer? I do that with a camel back on occasion, just carefull to freeze it 'in' the right side of the bladder to not gum up the flow and such.