I live in Florida too and I had this same problem. Unfortunately a larger IC isn't going to solve your problem. I have a 50' 1/2 copper IC I used to use and had the exact same results. The problem as mentioned before is the temperature of the groundwater you use is probably around or above 80 degrees. What I did was get a counterflow chiller, and used the copper IC to pre-chill the water. I get a 5 gallon bucket and fill it up with ice water, put my IC in that, connect my hose to it, and then run the water coming out of that through my counterflow chiller. It cools the water down to pitching temperature in 1 pass through, which takes about 3-5 minutes. Counterflow chillers arn't cheap though, unfortunnately.