FWIW, the ice trick has worked well for me, which is why I recommended it as a trick if needed during the the planned dash. I simply stuff it in available pockets, not encased in plastic. Saved my bacon on an IBA day while sporting an aerostich through the Badlands at temps well over 100 degrees. Evaporative cooling was my friend. Didn't have the potential horribles you mentioned, but I suppose they'd be possible . . ..
