Nah, 72 ambient is too high, due to the fact that the beer in the bucket could be as much as 5 degrees higher or so. IMO 72 for actual beer temp is pushing it. Sounds like you need a swamp cooler. Its cheap, easy to set up and nearly impossible to screw up. Given your close ambient temp is so close to optimal temp of 66-68, you would only have to pay the smallest amount of attention to it for the first three days, then after that it can rise to room temp with no issues. The swamp cooler was without a doubt the single best thing I did for my brews.